Heavy bleeding and clotting

Last night I experienced extremely heavy bleeding and clotting. I was laying on the couch when I felt this gush come out. I ran to the restroom and it was like a massacre. Of course I immediately went to the emergency room. I soaked 2 pads in less than an hour. Fortunately, my HCG blood levels are at 30,000 and the ultrasound shows my 12 week baby with a heartbeat of 161 per minute. The doctors can't explain why. All they said was that the bleeding was coming from the gestational gap between the uterus and the fetal sac. Has anyone experienced this?