I typically have pain or achy feeling in that same area. For a long time I thought it was my bladder. I finally realized that it was my rectal region. But, it's still worth it, if it continues for you or gets worse, to get a CT like patientspiders suggests. I also have a fistula (abscess at first). But, the pain was there for me before that too, so it's not necessarily related. For me it's the inflammation - that area for me is one big ulcer.
--40 year old female, dx as UC in '04 (1st symptoms in '03), switched to Crohn's in '05, 1 fistula, crohn's colitis, limited to large intestine --rejected (reaction/didn't work): Asacol, AZA, 6-MP, MTX, Remicade, Humira, prednisone
--Prochymal in Phase III study (can't wait til it's approved!)
--started Tysabri 3/21/08 => STOPPED 10/3/08 - now 2 months into it & it was the right decision
--currently taking budesonide suppositories, 3mg at night. Doing well with this so far. Dx Osteoporosis 10/08 waiting to start Forteo (pending approval)
--single mom to 11-yr-old girl