Someone please help me out here!?

Ok. I have been having abdominal cramps on and off now for about three weeks. I had light back pain and nausea and have been to three different ER'S. They all tell me the only thing wrong is I have a UTI [Urinary Tract Infection] I knew that already because I always get them but never have symptoms of it. Anyhow I think something else is going on here and even my dr said I do not have a UTI and did a ultreasound on my gall bladder. They seen nothing and did cat scans on my belly at hospital and also they seen nothing. Has anyone else had pain like this and found out later on there was in fact something? Right now I feel like total crap. I am on my period but feels like I have the flu but thats all normal I guess being on your period. Someone please help. I feel like complete crap and I just want these damn hospitals to do something for me instead of always sending me home. Also bladder problems run in my family such has bladder disease and etc.