i'm on my 3rd month of ovcon-35 (switched after 4 months on estrostep) and i too am having btb. i had it on the other pill every month as well. my gyn is doing a sonogram at the end of this pack. she thinks i might have something going on in my uterus.
is this your 1st time on the pill? they say it could take 3 months to adjust...unless you're me i guess.
hopefully your cycle will straighten itself out soon!