I got the antibiotics at the same time as I started my new pack of
birth control and took them both for the first week of my cycle, and I used protection until the next week when my antibiotics ran out (because, of course, things happen). I was freaked out and thought that the antibiotics may still have an effect on my normal birth control so I bought plan B that week and used protection regularly..
So now, its week three and I didn't use protection..