Sassy69
Generally speaking, if you are on hormonal birth control (i.e. controlled estrogen / progesterone levels), the general function of this tends to go directly against the reason most women use AAS -- to cut up & gain muscle, while estrogen continues to support estrogen-pattern fat depositing & water retention. For competition use, most girls will go off the b/c or use a non-hormonal method (e.g. IUD or condoms).
Also the AAS will usually interrupt your period in the sense that you won't get an Aunt Flo visit while you are on. Unless you've also got extremely low bodyfat (e.g. for competition, gettng below say 12%) which will also induce amenorrhea, expect your period to be interrupted until the first month after you are "off" and the AAS has worked its way out of your system.
But - does that mean you can't get pregnant? Well, you can still ovulate even if your flow isn't there. Does your b/c work? Actually I don't know. I think I would suggest a back up method while you are on tho -- you are mixing your hormones - no guarantees.