Thank you for your query.
Actually two factors have compounded here, leading to altered bleeding.
First is that you missed a pill.
Secondly is that some antibiotics frequently react with birth control pills and reduce their efficiency
Hence, you could be facing breakthrough bleeding
due to decreased efficiency of the pills.
Right now, you should test for a pregnancy
if you have missed your routine period as you had unprotected sex meanwhile.
next step would be to consult your health care provider, and restart a fresh pack sincerely, after ruling out pregnancy.