OCD Wondering

Hi, I'm a 16 year old girl and I was just wondering if this sounds like OCD to you because it sort of matches the description but is different in someways.

Ever since I was little, I've been through these cycles of obsessions that can last for a few weeks, a few months or even years. My first one was always thinking that every question I was asked was a test and my answer would determine something about me. (For example if I was asked if I wanted Pizza or Fish fingers for tea I would think that if I answered wrong it would mean I was going to die) but I'm not sure if that was just an immaturity thing. When I got to about 6 I became obsessed with my weight and would constantly be comparing myself to other children, weighing myself and seeing if I was average ect. This used to upset me quite a lot because I was bigger than other children. This has gone on through all my life but now I just think of it as an "i'm a teenage girl so I'm meant too count calories" thing.
Then as I got to about 9/10 I became obsessed with cancer and diseases. This was really stressful and went on and off until I was around 13. I would constantly be examining my body for symptoms, googling things and asking other people for reassurance. I'd also be paranoid about family and friends. If someone even coughed, I'd straight away be having a panic attack and thinking that they're literally going to die. I'd make bets with myself like "if I get home in 34 steps then I don't have _____".
Then from about 13-14 I got what I think is called "HOCD" where I was obsessed that I was a lesbian and the thought terrified me. (I'm not homophobic and I don't think there is anything wrong with gays.) I literally hated myself through this time and this was my worst obsession so far. I spent all my time thinking about it, feeling ill, even getting to the point of throwing up. I made bets with myself, stopped eating for a while, googled everything, couldn't go out and even thought of killing myself at points. (I never would do that now, though)

At the moment I'm don't have a proper obsession but I do occasionally have intrusive thoughts a few times a day (Family members dying is the general thought). When I do I've started to repeatedly knock on wood and if no one's around I'll do it to the point my knuckles hurt and hands ache. Another I do are count calories on an app and make sure I keep below a certain goal everyday.
Other things I've obsessed about are growing up to be a murderer, car crashes and I used to get these random images of myself in my head doing really inappropriate things.

Sorry, I rambled on for AGES but it really scares me when I get into a proper obsessions and the few people I've actually told don't tend to take me seriously. I'm just hoping if I know what this is then I'll be able to control it better and sort my head out. Thanks.