On Wednesday 18 December, I went for a colonoscopy. Is it possible to get my period afterwards, maybe from the anesthetic? I should not be having it now, but only in about two and a half weeks.

Your menstrual cycle should not be interrupted by a colonoscopy.

But stress can affect it right?

Stress will affect it more than a colonoscopy will. So will age. Age is a very important factor you did not include.