I had tonsillitis and was put on penicillin for 10days, I stopped taking the pill. It has now been 15days and I still haven't come on could I be preg?

Menses irregular. Acute infectious conditions can alter your menstrual periods regularity. If you think you are pregnant get a home kit and use the urine test strip to check. But wait a few more days. This may just be due to the tonsillitis.