I have had extreame back pain for as long as I can remember I have had xrays and m.r.i's but it shows up with nothing.

Ive always had iiregular periods and when I get my period its normally very heavy and lasts about 8 and I get extream cramps
I went on the pill for abit and it made my periods regular but then i run out and when I started back up on it I got my period for a whole month!!

Also twice I have woken up with a really sore stomach it actually felt like a opened can was trying to rip out of my lower stomach, the pain was so bad I ended up passing out from it

I have been to the doctors and it felt like they just blew me off the looked at me and said because im young (17) they cant do any thing but give me pain medicine which Id rather not take

Any ideas what could be wrong?