I am so sorry that you are having to go through this ordeal at such a young age. It's bad enough on us "old timers".
You have a right to be frustrated and venting on this board is a good way to get it out.
Now, things will get better....you will just have to have faith in that. You mentioned that you had been feeling better so you know it is possible.
Something has upset your system. It takes a lot of detective work to figure out what's causing the problem. I would suggest keeping a food diary. Maybe there might be some different meds you could take. I'm a "D" so I can't give you much info on "C" but have you tried probiotics?
Believe me, I understand thinking about your stomach 24/7....it's no fun.
I went out to lunch today and ate way too much and now I feel like a beached whale. Took some Alka Seltzer and maybe that will help. I'm sure I will pay for this later.
Anyway, you are not alone and we are all here to help you through this. Don't give up. You will have good days again.