I was terrified of my colonoscopy but it was FINE, I had an endoscopy at the same time! The prep is the worst part but there is no vomiting. You can ask for anti-emetics in your IV beforehand so that there's no risk of you being sick. I felt lovely after the procedure (obviously I went for ALL the drugs!).

I suffer from chronic d* and that's why I had the colonoscopy done... turns out there's quite a bit up (nothing too serious), so well worth the prep!