Freaking out! Need advice!!

Im 12 weeks pregnant and yesterday I felt like I had to pee (pressure on my bladder) when I sat down a huge blood clot fell out of me and when I say huge I mean huge, so huge in fact I thought it was the baby and I started cramping and bleeding. At that instant I thought I lost my baby and went straight to the emergency room. They took me back and did a ultrasound and saw the baby moving and kicking with a healthy heart rate of 160. It's been a day and my cramping has stopped but I'm still bleeding a little bit. I also had what I thought was a period in March, it lasted as long as my periods normally do and it was as heavy (I was 4 weeks pregnant and didn't know it) so my question is has anyone ever experienced anything like this?