Mallory - dont worry hun (unless you are hoping for BFP?). They have done extensive tests using antibios and placibos, and there is no significant effect on BCP absorbtion when taking antibios - the pill is absorbed quite quickly into the bloodstream. Some are contraindicative, but they usually say on the packet. Interestingly, St Johns Wort (used as natural anti-depressant) affects absorbtion of the pill.

Like others have mentioned, it is mainly if you are vomitting after taking the pill, or if have diarrhea that may affect its effectiveness.

Good luck for whatever result you are hoping for!