If you had two pregnancies on other birth control, and might be pregnant again, I think you might want to check out a book like Taking Charge of Your Fertility by Toni Weschler or Your Fertility Signals by Merryl Winstein. The first is the Fertility Bible and the second is like the CliffsNotes version. That way, you can start to recognize times when you might possibly be fertile, which is when any birth control you might be taking would fail anyway. And if your cycles are very regular and such then you might not need another form of birth control anyway--if you practice the "fertility awareness" correctly it works just as well as if you take the pill correctly (although, of course, most people don't quite get to perfection). At the very least, you might have more of an idea of whether or not you ARE pregnant because you'll know what your cycle has actually been doing, since a lot more happens in a month than just period or no period. The books make it so much less of a mystery.
Either way, I hope it works out well for you. It sounds stressful! I hope you're all right and can work things out as easily as possible. Good luck!