I had one. I felt nothing, and I remember nothing. I took an anti-anxiety medicine my doctor prescribed for me. I took two 1 mg pills as perscribed two hours before. I had an IV put in, and I went to sleep instantly.
It took me two years to get a coloscopy because of fear. I have colon cancer because I waited two years. For anyone who is afraid of colonoscopy, I can assure you there is zero pain. In fact the day after I felt better because they cleared some clots out.
Please find your strength. If you have anxiety speak to your doctor and get a prescription for it. According to YALE never buy prescriptions online.