Possible miscarriage ?

UPDATE!! It was infact a miscarriage.

Firstly I'm 7 weeks pregnant. Had my first ultrasound yesterday every looked fine. Baby's heartbeat was beating great. Today I noticed Everytime I would wipe it would be very light pink. Called my ob, the nurse said everything was okay. Later on I started to cramp off and on nothing to bad. Then I finally decided I'm going to go into the ER. Right before I go, bright red blood started running down my leg. I go & it gets much much worse.. I'm passing blood clots & I can't even change a pad quick enough before there's more blood everywhere. I got blood tests ran, another ultrasound both regular and vaginal. Seen a heartbeat so everything checked out fine..sent me home. What is going on!!!!!?