Hello! :)

I just wanted to post to this forum because I'm very worried. 
For most of my life I've suffered with nausea and sore stomachs, mainly diagnosed as anxiety. However I'm very worried, it's gotten worse and harder to cope with, and over the course of a few months at the start of this year I lost 10kgs, maybe even more and I can't gain them back.

I've lost a lot of appetite and struggle to eat a lot, and usually feel sick after eating. I've also been constipated for years, I only go to the bathroom a few times a week and it comes out small and pebble-like. I've also had a bruised-feeling tailbone for a few months which is why I'm now convinced (alongside the bowel habits, nausea and weight loss) that it's some sort of colon cancer. The tailbone hurts to sit on and I have to adjust during car rides because it causes genuine pain when bumped.

I've had many tests over the years to try and figure out what's wrong but still no answers. I've had tens of blood tests, medication (which doesn't work), a barium swallow/x-ray, and an endoscopy (all came back clear) However I haven't had a stool test/colonoscopy, so I suggested it to my doctor and when I return home from being away at school, she said we'll have an appointment then and figure out what to do.

I'm just really scared and anxious, I know it's unlikely for someone so young to get colon cancer but many of my symptoms match up, and it doesn't quite fit the profile of either IBS or Crohns (IBS there's no weight loss, crohn's is diarea not constipation) so I'm just really scared :( My quality of life is so down at the moment due to these mysterious symptoms that have lasted years and years. If anyone has any advice or anything at all it would really really be appreciated. Thanks so much :) ps- sorry if this is long!!