Pressure in my rectum

I had robotic surgery on Sept 21 and my uterus was removed. I had two big fibroids that the doctor said were pressing on my spine and causing all the pain I had been feeling in my legs. After surgery the pain went away and I thought I was on the road to recovery. But on day 5 Post Op I began to experience the worst nausea of my life. It lasted for 2 1/2 weeks. My GYN doctor sent me to a gastroenterology doctor who did a scope and found I had an ulcer. I am still having extreme pressure in my rectum and now am going to have a colonoscopy. The doctor said I have to wait 6 to 8 weeks before they do it. I am wondering if any if you have experienced this type of issue. The pressure is driving me nuts and my bowels are very loose. Any advice would be so appreciated.