What the hell do I do ?!

Okay .. So I haven't had a menstral cycle and I've always been irregular . But I this time I haven't had a cycle in 6 months .. I wake up every day with stomach aches , I have little to no appetite most of the time . I've taken urine pregnancy tests and they were negative . I went to the ER and all they gave me was nausea medicine !! Even visiting an OBGYN got nothing resolved . I was told to try birth control to see if that helps , but I've been told by a lot of women who actually have kids that I may be having a "undetectable" pregnancy because they definitely believe I'm pregnant . Even my grandmother !!  My current boyfriend and I have been together for a while , but we just started having sex back in July . I can't go on with this cramping , stomach aches and nausea .. Some one please tell me - what the hell do I do ?!