What Causes Heavy Vaginal Bleeding During IVF Procedure?

Hello. I had 3 embryos transferred Mar 9,2015 and I was constipated and bloated. The constipation is gone now and bloating is Goin away too. I have had heavy bleeding for the last 2 days my dr said that bleeding is common for IVF but I am still worried. I am still goin to bathroom frequently but the bloating is leaving is that maybe becuz I am no longer constipated or was it due to procedure