I firstly just want to assure you that you are going to be just fine. I know what you are going through because I have been there many times. IMO you do not have anything to worry about, just perhaps something to fix, like your diet or your anxiety.
What I have learnt over the past 10 years of seeing many doctors/GI specialists and obsessing constantly over many GI issues, digestive problems, nausea, weird BMs, having a myriad of tests done, often...is that stomach issues are actually very common and they can go on and on and on... But it doesn't mean they are sinister! And they are made a lot worse when we focus on them. I know this well from experience.
My thoughts would be that you may need to change your diet in some way. A colonoscopy is prob a good idea NOT because I think you have CC, but to check for things like celiac, lactose intolerance, all sorts of digestive issues, again let me stress NOT because this could be CC.
You could (unlikely but *could*)have something like crohns or inflammatory bowel disease which would also be picked up on a colonoscopy, but honestly even those are rare when you think about how many ppl have the exact same symptoms and problems as us and never end up getting an actual disease as a diagnosis.
Dan you're ok, it's highly unlikely that you have anything even remotely close to CC going on. Please try and keep calm. Breathe. You're just fine.