What Causes Heavy Vaginal Bleeding While Breastfeeding A Child?

I am ttc so was testing to see when I ovulate and it was on 17/18 March so we had unprotected sex on both those days. Yesterday I woke with very heavy bleeding and its even heavier today I'm having to change every 1-2 hrs when usually I change twice a day. I have never had to change during the night but last night I had 2 change twice. I have been feeling really bloated and crampy the last few days as well. I'm also breastfeeding. I am assuming its my period come early and extra heavy what do you think??