If you have a good relationship with your doc, by all means keep it up. The scope would probably be a good idea, with your history of hemorrhoids and rectal pressure, and because of your age. Do you not have a uterus because you had a hysterectomy? When was the last time you had an ultrasound?
A friend of mine ended up having TWO uteruses and, yes, TWO cervixes. Very bizarre. She had surgery to fix this crazy congenital condition...we'll see if she'll be able to have kids. I'd be very interested if you've had cervical/uterine issues in the past!
As far as the gas, this might just be regular changes in your physiology, but a sigmoid/colonoscopy will still be a good idea for you. The only difference is how far up into the colon they place the scope. Have they explained why you're not receiving a colonoscopy, by any chance?