When I saw a G.I. the first time, I had a colonoscopy and endoscopy run the end of that same week. The last time I went to a G.I. (a different one), she had me scheduled for a colonoscopy one a week later.
I'm highly suspicious of why they would want to wait three months, especially if another doctor thinks you have polyps. I think you are getting inadequate health care. I notice no one said anything about testing your gall bladder. If you have a stone lodged in there, that can be the cause of your pain, bowel problems and fever. And that can set up a dangerous infection if left untreated. If your problem is from erosion of the esophagus, then three more months of acid reflux is only going to damage it worse. And we've already discussed the importance of having polyps checked.
No, you should not have to wait three months to have a colonoscopy. While the best G.I.'s are booked well in advance for appointments, they usually have no trouble getting your tests done in a reasonable amount of time because once you're in, you get first priority. And less popular G.I.'s have even less waiting time. I think you need to find someone else who is willing to get this stuff done and not leave you to suffer needlessly for months on end. I'm wondering if this doctor hasn't put you off because he thinks you're somehow faking your symptoms or are crazy and his plan is to put this off so long you'll lose interest.