Anxiety or something even more serious?

I have a great problem that has been bothering me for over a year now, and I don't know what to do aynmore cause I haven't been happy or felt safe for a very long time. I guess I'm a coward because I can't face some things so I'm going to write down my story. I have to apologize because I might make some major grammar mistakes but onsider that english is not my mother tongue. Thank you a lot.

So, I'll begin this story with a situation that triggered all of this. I'm a 23 years old guy from Europe. It was a Saturday night (late 2012) and I just woke up feeling really hangover beacuse I partied the night before. I was laying in my bed, surfing the Internet and at one point I randomly saw an ad or an article about some serious disease. I can't tell what it was about (maybe leucemia, cancer, hiv or something like that) but it made me think. From NOWHERE I started to think about it until it made me feel really uncomfortable. I was feeling very dizzy and strange because I drank the night before but still I tought that feeling that way means that I have some serious disease and that I'm going to die soon.
That thought is trapped in my head since then. I have hypohondriacs in my family, I red that if someone in your family has that type of mental ilness there is a great chance that you will think the same way. I have hypohondriacs from both sides of my family, moms and dads, some of them are pretty extreme about it.
At that time I was in a relationship with my ex girlfriend, we have been together for years, had our ups and downs but then everything was kinda normal and okay with us. I was staying at her place almost all week even though I was torn between my own family, her and my other obligations like college, work and projects I've been working on. The distance and money were the main problem so I was feeling pretty stressed from time to time because I wanted to make balance between all of that (but it never worked, everyone was mad at me because I didn't spent enough time with anyone, but I couldn't clone myself, I was with them almost everyday).

I told my girlfirend about my problem and my overthinking and all she said was „You are crazy and nothing is going on, just shut up about it already“. I couldn't help myself so I starded Googling sympthoms, and that's probably the worst thing I could to to myself. I red about some basic sympthoms that almoast every disease have in common, like swallen nodes, feeling tired, a cold that never goes away, rash, headaches, fever, etc… Two weeks after that were a pure hell for me because I started to think about all those sympthoms, my heart beats would go crazy, I would turn red and start to sweat heavily, I was close to a panic attack. And it happened on a daily basis for the next two weeks. (late 2012)

I have to mention one thing, and that's a situation that happened year before all of this (2011). My sister (13 years old at that point) had a cancer that started to modify her face. When we realised it my family was crushed and I was the only one strong enough to stay calm. I talked with all of my family members and told them that she is going to be okay while they were devasteted, crying all the time. I didn't cry and I couldn't cry because I developed some kind of a defense mechanism to stay strong and don't let bad thing destroy me as a person cause I'm very emotional and emphatic. I made it then but I think that it came to my head months later, the day I started to overhink. That day I red an article on the Internet I also remembered about my sisters cancer and how it could happen to anyone. If it happened to a 13 y/o girl that is good at sportist, a good student and a kid anyone would be proud of, why wouldn't it happen to me?! It made me think even more.

Back to the main topic. So that two weeks were extreme. I couldn't do anything but think about how am I going to die. I even started to have some sypthoms I saw on the Internet, like a cold, I started to feel dizzy like I had a fever but didn't etc. I just couldn't stop, it was terrible. I even started to sweat or at least I started to notice it because ever since I was a kid I had sweaty arm pits, palms and feet.
After that I said to myself that it's okay, if I have to die I'll die but didn't have the courage to visit the doctor. I continued my life but with a really heavy weight on my back… My own terrible thoughts that are always somewhere behind me.
I was finishing my last year of college, I didn't have much to do so I decided to work some physical job just to use my student rights while I can. That job was terrible, not my first time working there but I couldn't find anything better. It was all about waking up at 5:30am, people were rude, I would come home after 8 hours and went to college till 9pm. It was really hard for me but my parents told me that I am a pussy because I can't endure it. It was a devastating thing to hear and I didn't want to dissapoint them so I continued. The tempo was hard, even harder with my bad thoughts. I started to look for changes on my body, like I would WANT to find them. I started to touch my nodes and while I was thinking about them they started to grow. I actually always had bigger node under my right hip but I never took it serious until then. I started to touch it every day just to feel if it was still there. Taking a shower was a nightmare because even if I had a good day I would pass thorugh it with my hand and remember all the bad things. I started to go crazy again. I was constantly thinking about potential sympthoms and then I started to have a runny nose. My sinuses are sensitive since I was a kid and changes in weather affect them a lot. But this was slightly odd because I would woke up and my nose would be full, ONLY in the morning when I woke up at 5am to go to work. The rest of the day would be normaln and nothing would drip out of it. I reaised that I sweat when I'm cold, my feet, palms and under my armpits. It wouldn't last fot too long, just when I think about it I would start to sweat. It didn't feel right.
On that job I didn't have to use my brain at all so I was overthinking all the time about potential situations etc etc but didn't have the courage to go to the doctor. I'll fast forward to the end of summer 2013. My sister got diagnosed with cancet again and she had to go on a terrible surgery again. I was devastated and couldn't handle it anymore. My depression became worse and I didn't feel like doing anything. My girlfriend hated my family and she wasn't any support about it, she was even rude. I'll never forget one situation while I was driving us home, and I started to cry. I told her I can't hold it in anymore, she is my sister and she doesn't deserve this… What can I do?? The only thing she did was – YAWN and turned her head on the other side.
My sister was in a hospital and one day while I was going home from her I had a panic attack in the bus. I came out of the bus, walked and it was okay, decided to go on another bus and had another panic attack. I couldn't bare with people, I started to sweat, my vision was blurry and I just had to go outside.
Two weeks before my sisters surgery I found out that my girlfriend, the only person I truly trusted and felt confident with was cheating on me. I was devasteated, I had a blackout for the first time in my life and another panic attack. We broke up after 5 years of beautiful relationship.

Thankfully, my family was a great support, and they were with me while I was devastated. But sisters surgery was way more important than that and I wanted to focus on it. Everything went okay and she is safe now! I realised I have lost weight, not too much, around 5-6kg in a couple of months. I started to eat healthier but my mind always told me that it's because I have a serious disease, not because I quit on junk food.

After a breakup I started to have nightmares and once in a month I would wake up sweaty (only when it was about my ex). I have never had nightmares before. I was feeling slightly sick for a long time, actually I only had a runny nose and a sligltly swallen lymph node ( I guess it is a lymph node) on my neck, under my chin on the right side. I wasn't feeling worse at all even though I worked my ass of all the time ( I red than one oft he common signs of a serious disease is feeling weak all the time, I didn't). Then came a period when I decided to occupy my thought as much as I could just to feel better (late 2013). That was a wrong decision too.

I worked that crappy job, I was feeling tired after my job, that's the usual but I wanted to go out, hang out with my close friends, party and meet new people. I kinda quit sleeping beause laying in my bed was the worst part of the day. I was trapped with my own thoughts and it was crazy. I would start to think, anf think until I started to sweat and feel very nervous.