worried I may have ulcerative colitis

I am starting to get really worried about what might be wrong with me. I have seen doctors about 4 times in the past couple months, had blood tests and stool tests and gone to the hospital. I am extremely anxious all the time and tend to over think things so its likely I don’t have ulcerative colitis but I’m still paranoid. I’ve gone through many phases of telling myself I have different things wrong with me. colon cancer, Crohn’s disease, appendicitis but no doctors have been worried about these things.

My symptoms are constant nausea, diarrhoea, constipation, stomach pain in my lower left and right sides and between and underneath my ribs and my stomach is constantly making really loud noises, not the normal noises. This started with diarrhoea every day about 3 months ago, and the pain and constipation has been going on for about 1 month. the constant nausea had been happening for the past 4 years of my life but has gotten so much worse this year. I also had a black stool a few days ago which I know is a symptom of ulcerative colitis but I haven’t had blood in my stools (that I’ve noticed). the main reason I’m worried about having this is I really don’t want a colonoscopy. the thought of it terrifies me, everything about it. taking the laxatives, going under anesthetiser and having to be naked in front of the doctors (I know it’s their job and they see it all the time but it just really scares me)

the doctors believe I either have celiac disease or ibs and they are making me eat gluten for 6 weeks and then getting my blood tested even though I’ve been eating the necessary amount of gluten this whole time.

anyway, I was just hoping someone on here could give me some advice or help me in any way. thank you :)