InPain, I have some experience with chronic constipation from pain medication. I was put on MiraLax, but when it became OTC my insurance would no longer cover it and I can't afford it out-of-pocket. I now take an herbal remedy, cascara sagrada capsules. I only need one a night, but you would probably need more. It works by the next morning for me and is a lot more natural than Ex-Lax or those types of laxatives. Stool softeners don't work for me. I have a hard time whenever I have surgery and am on heavy pain meds. I tell them that I need magnesium citrate and they try everything else (which doesn't work) until they finally order that for me. I once went without a BM for 7 days and was so bloated and miserable. When I finally got the mag citrate, I drank 1 1/2 bottles and filled up 2 bed pans with BM. The last time I had to have surgery, I took my own mag citrate with me and drank it after not going for 5 days. It worked. So you might try that, too. It is OTC in any drug store and even comes in cherry and grape flavors.
I think it's important that you get to the root of your problem. However, the not wanting to bear down to move your bowels after the hysterectomy probably contributed to your present problem and now it has snowballed. I had a similar problem after 2 hernia repairs. I do not have IBS or any other bowel problem.
Another point is that you only have one small meal a day. There may not be enough food to make its way through you on a regular basis. You also need a high-fiber diet.
I am assuming you are on SSI. You do not have to be elderly to get Medicare if you are deemed disabled by Social Security and benefits are based on your work record. From what you have told us, plus your age, I'm guessing you didn't have enough work history contributions to qualify for SSD and Medicare.
I hope all this helps a little, but I agree that you need to see a different GI doctor.
Hugs,
Connie