C.A.
Hi S.,
I am not a Dr. but they should have told you to use an alternative method of birth control because of the antibiotics. Many of them decrease the effectiveness of birth control. Call your OB office and ask them if this is the case with Bactrim. You might possibly be pregnant. I also do not know the effect of the BC on the HPT. You might also want to ask them that.
Good luck,
C.