Fluid Back Up in Colon

After being on a fluid diet recovering from jaw surgery I transitioned into soft foods Aug 1 this year. That is where all my digestion problems started. On Sept 1 I have been on a normal diet. Basically, my body cannot produce a bowel movement. The only way I can is from Sennokot or Milk of Magnesia. I've suffered with alot of bloating, cramping, pain, gurgling on the left side where the colon is. When I did have a bowel moverment it was black and looked like mud. I was slightly anemic and tested postive for blood in the stool about two months ago. This has affected me limited in that I can't  eat or drink that much and feeling very fatigued. This is always a constant thing. I've had a colonoscopy, blood work done. Sometimes the fluid back up is trying to get out but it can't for a while and I have very sharp pains in the lower abdomen. I had a CT scan done at the hospital that was normal and it showed that I had a liquid back up in the colon and they just gave me a laxative that didn't work. Now, I'm not anemic and when I have a bowel movement it's light brown and yellow diarrhea. The GI specialist and my primary doctor said its irritible bowel syndrome. I've tried Amitiza and I have a healthy diet. Currently, my body is unable to produce a bowel movement and my rectum is prolpased. I am using Sennokot which hurts my stomach. I've had a fluid back up for a month. My doctor told me the fluid back up into my left abdomen and backside is normal of IBS. The liquid always makes a gurgling noise. My doctor prescribed me Paxil which made me very tired I had to stop it after two weeks. It didn't help. Whatever fluid I drink goes right to my colon on the left side and it backs up into the right side and the back sometimes. It's alot of disconfort it hurts me when I walk or move around anyway. I drink fluids but not alot. With the two laxatives it takes them several hours of a few days to work and they both hurt my abdomen and the whole area around. I'm a 25 year old female. I never had any problems with digestion until the past four months. Its pain and discomfort. If its IBS does anyone have any suggestions on what they know or has worked for them. Any suggestion I would be so grateful for. Thank you.