My birth control also has a very low effectiveness.
Hi,
Well if you just had sex and you are supposed to start this week it wouldn't be the most fertile time, but still somewhat fertile and everybody is different. I would say if you are on birth control and haven't been missing any, that you shouldn't be pregnant. Just remember two things, Many women have become pregnant while on birth control pills, and that pills don't protect against std's. Which I'm sure you already know, just reminding you :) Not sure why the burning though. If you don't start this week, take a hpt but I think you should be ok. Good luck to you and let us know how it goes.