So my question has to do with now antibiotics interfere with birth control. I'm basically wondering if I need to start my new pack of BC immediately (just started period) or if I can wait until Saturday when I would normally start the next pack. Here is now my last week has gone:

Last week I was put on an antibiotic for a UTI.  During the course of taking my antibiotic, I had sex forgetting I would need an extra form of BC ... so, I got Plan B and my period started the next day anyway (as it should have). Do I start my next BC pack immediately, or do I still wait until Saturday?