Thank you for your query.
No , penicillin will not cause an abnormal menstruation
. There has to be a different reason for your menstrual problem. Infection of the womb may cause abnormal menses , and there may be a connection between that and your strep infection , in which case the penicillin might help. Also be aware that antibiotics may interfere with the absorption of the contraceptive
pill and in that way interfere with cycle control. If your bleeding does not disappear in a week please consult a doctor.
I trust this information is helpful.