Abdominal pain and lower back pain; lower left quadrant; 17 years old

I am 17 years old, 200 lbs and 6'2", and I have been having abdominal pain with some lower back pain on my left side and it goes across the middle and barely the lower right quadrant. Feb 7th 2009, I had my gallbladder removed because it was not releasing bile, it was barely working @ 4%. After surgery I was feeling fine; each day I got a little better. But right when I thought I was back to normal I began having these pains. They are very sharp and sudden, once and I while I know when it is going to happen. They also seem worse after I eat, but on the other, hand I have had moderate sudden pain without eating. My doctor put me on Bentyl and Miralax; The Bentyl helps a lot, the laxative I am not sure about because it doesn't change my bowel movements much. 2 weeks ago, I was taken to the hospital in an ambulance from school because of the severe pain, they gave me a cat scan and nothing showed up. Next, my doctor had me get a lower bowel follow up, once again, nothing showed up. The last thing my doctor wants me to have is a colonoscopy. I plan on having one asap. I was wondering if anyone had any Ideas on what is wrong with me. My gastroenterologist is running out of Ideas. BTW, I also have Eosinophilic Esophagitis and asthma. Please help me by giving me ideas on what I may have, if you have any.
                  
                   Thanks, Fred