heavy bleeding after having sex while on period

My fiancé and I had sex while I was on my period (day 4 of my period). Before we had sex my period was very lite. After we finished I was bleeding so bad and had horrible blood clots. We've had sex while I've been on my period before but the bleeding afterwards has never been this bad before and I've definitely never had blood clots. I am wondering if anyone has had this happen as well.