26 yrs old - No periods.

I have always had my period since age 13. Slightly long cycle but it always came. Over the years trying many different forms of birth control didn't effect it much ever. Now (of course when I decide to try to have a baby) I haven't had a period for 8 months!!!! Not pregnant despite many tests about every month since the 3rd missed period. I get the whole "if you stress over getting pregnant too much it makes it hard to actually get pregnant" thing that everyone says, but my periods just stopping??? I have not changed my diet, exercise, or anything else significant the I can think of in the last year. Why could this be happening?? OBGYN just wants to put me on BC to regulate which doesn't do me any good when I am trying to have a baby. Any ideas????