WebMD lists several drugs that could reduce the effectiveness of birth control, These drugs include: many antibiotics (e.g., cephalosporins, chloramphenicol, macrolides such as erythromycin, penicillins, sulfas), aprepitant, bexarotene, bosentan, dapsone, felbamate, griseofulvin, certain HIV protease inhibitors (e.g., amprenavir, nelfinavir, ritonavir), modafinil, nevirapine, phenylbutazone, rifamycins (e.g., rifampin), many seizure medications (e.g., barbiturates, carbamazepine, phenytoin, lamotrigine, topiramate), St. John's wort. I have heard of migrane medication effecting birth control but i really dont know if that is true. If your doctor didnt say anything I wouldn't think that there is a problem.

If you dont start, take a pregnancy test, if it is negative, start the new pack, it could be that you just skipped your period, you may still start but it is unlikely if you didn't while on the placebo pills.