With every bc pill i have lots of breakthrough bleeding up to 2 weeks before period. this stops when on antibiotics any ideas what could be causing it?

Breakthrough bleed: Sounds like breakthrough bleeding which occurs when you have bleeding at unscheduled times while on the pill. Often things get back to normal the next cycle. If not then schedule a visit to discuss changing brands or changing birth control methods. This is very common. Other than being annoying it is not dangerous. Why not try a different birth control method since this keeps happening.