Threatened miscarriage

I'm 8 weeks 3 days pregnant. A couple of weeks ago I had some light brown discharge but it went away a couple of days before my first obgyn appoinment this past Friday. The ultrasound was fine the blood tests came back fine but this morning I woke up and blood had soaked through my underwear to the bed. Like a really heavy period. I peed and a blood clot came out. I thought I had miscarried. I went to obgyn and the baby is still alive! Heartbeat the same as Friday, 167. They said I could still miscarry though. I'm also negative blood type, so that's a concern too. Has anyone else been through this?