Does Antibiotics Cause Heavy Bleeding During Menstruation?

hi, i am 22 yrs old and i been on my period for 3 weeks now. It's heavy and black-red blood, with some blood clot. In the beginning of my cycle i was also taking an anti-biotic called amoxicillin. Now sense I'm done with the pills, my period is still on and Heavy! what could be the problem?