How do i know if i have endometriosis?

i have had unprotected for the years on end with no b/c and no other kind of prot. Never gotten pregnant. In feb of 2004 i took myself to the er for my " period" I was 2 months late for my period and all tests came up neg. then i finally got my period nad it lasted for 3 motnhs straight, heavy and lots of clots, so finally after my doctor suggested i went to the hospital, where they ran tests and said my hormone level was off and im lucky i didn bleed to death, my bllod level was at half of its normal number. Well they put me on b/c to stop the bleeding and i went back to normal after that. december of 2005, i went back to the hospital because i had very sharp pains in my lower abdomin, the kind that made me unable to move just double over in pain and cry!!!! they did a pelvic exam and said i should just take some ibuprofin and get some rest. i never had the pain again.....i ust found out im anemic from 2004 still.... could i have endometriosis, how do i know for sure?