Stomach and weight issues, anxiety is ruling my life

My weight over the past 6 months has shot up 15 pounds, primarily in my stomach and I have had awful stomach issues (IBS symptoms, cramps on my right side that I have convinced myself is liver failure), etc.
My anxiety brain tells me I have some underlying medical condition, even though my doctor thinks the anxiety medication will help my stomach problems. My rational and educated brain tells me I KNOW cortisol levels increase with anxiety which can cause weight gain and belly fat. It can also cause IBS type symptoms. But I can't shake the nagging thought I have something wrong inside and that I will need surgery or have some life altering illness. I am consumed and obsessed with it.
Then the frustration sinks in. Am I feeling this pain in my stomach because I am obsessing on it so much? Is it even real? It hurts worse after I drink, and then I am positive its my liver or gallbladder going out. I have been good about not googling though so that's a plus.
I was prescribed Buspar again which I start today and have a follow up appointment in 4 weeks. I am going to try to keep working out, meditating, let the meds do their thing, and hopefully the stomach issues will resolve on their own.
About 3 years ago when my anxiety was at an all time high like it is now, I had all the blood work, scans, etc. you can think of and everything was normal. I am relatively young (28). I am trying to tell myself that the odds of having something life threatening are slim, but my OCD is consuming my life. I had a bad breakup and for the past two years didn't take the best care of myself. I partied and drank a lot and ate terribly, which is why I believe I have done irreparable damage to my body internally. I am a full time student and work full time so my stress is monumental. On top of that, I recently discovered I am being stalked by an ex boyfriend who has a violent criminal past.
I just needed to get this out and vent and maybe relate to someone.

Anxiety and stress manifest in different ways, IBS and stomach issues are in fact common. When my mum passed away and my dad had a bad heart attack I suffered similar symptoms to what you described. I had also started a new job etc.. And so stress ws way up. I know it is not easy really, I've been through it. However let us first start by thinking positive :)

Something which I wrote in practically every post is to relax by listening to some classical, chillout or Enya type music. Exercise is also very good, since when we do exercise, our body releases endorphins that create a sense of well being.

If required do not be afraid to seek professional help. I would avoid medication ( as it can be worse) and consider cognitive therapy ( talk therapy) with a psychologist.