Yes, antibiotics do cancel the effects of hormonal birth control. That is why it's best to use condoms for the duration of at antibiotics and up to two weeks after, to be safe. I am very surprised your doctor did not discuss this with you when asking what medications you were on before prescribing the medication.

Regardless of what the results say, it is great that you have some really awesome support. This has got to be a rough time, and I imagine that helps immensely. Try to relax until the results of the blood test come in (I know that's a lot to ask, but it would help things a bit), and go from there.