I am having similar problems. I conceived in jul 04 and had a successful pregnancy with baby born mar 05. I am just now trying again and in oct my period disappeared and never came back. Doc prescribed provera and that worked... 3 days after completion period came. (they may need to up your dosage or have you take it 2x's day) but every test I use to test for ovulation is not detecting anything. I dont think I am producing enough of the lh hormone to signal ovulation. I feel so helpless.
Like you, I was on the pill since 17 and I am 25 now.
I hope you get good news soon...