My main problem, in addition to going to the bathroom around

My main problem, in addition to going to the bathroom around 20 times every 24 hours, is constant pain and discomfort of the urinary tract when I'm not urinating. I have been to urologists and ob/gyns. I have had hydroextension of the bladder, and it showed I don't have cystitis. I don't have incontinence. I do have a cystocele and prolapsed uterus. One doctor said I should get a hysterectomy and bladder tuck; another advised against it and put me on Detrol LA and Premarin which I've been taking for almost 2 months...no help. My discomfort has gotten worse. It's worse when I sit then when I'm walking around. No one seems able to diagnose this problem, but I know something is wrong, and I need to get relief from the constant pain. Should I have an MRI? What is this condition I have and what can cure or relieve it?