heavy bleeding, 8 weeks via IVF

Last night, I was in the emergency room. I started bleeding profusely and blood was just dumping out of me. I thought for sure I had miscarried. I went in and they said it looked like a lot of blood. They weren't hopeful. My pants were soaked and I was bleeding through the puppy pad within 15-20 minutes. They did a sonogram and the baby was in there with a high heart rate. The uterus was filled with blood. They don't know what caused me to suddenly start bleeding. The original hematoma is so small, there is no way it caused all of the bleeding. Anyone have any experiences with this? I'm 8 weeks pregnant via IVF