If i am on the pill & had breakthrough bleeding, is it likely that i may be pregnant if i don't get my period during the sugar pills?

Not very likely: When a woman is on bcp and has break through bleeding, sometimes she won't bleed when she's on the sugar pills. Often break through bleeding can be caused by taking the pills late or missing one or two. The first time this happens - not bleeding on the sugar pills - i recommend a woman check a pregnancy test just to make sure.