Missed miscarriage

Thursday morning I spotted very lightly. Thought it was okay to have minimal bleeding. Later that day I had bright red bleeding but still little. Didn’t feel well. Went down to ER (I work at the hospital). Did ultrasound and there was a heartbeat. Went back for an ultrasound yesterday and there’s no heartbeat. Fetus measure 5 weeks 6 days on Thursday and yesterday at 6 weeks. What are the chances that I really miscarried? Idk if I’m in denial but what if they missed the heartbeat? I’m supposed to go back for an ultrasound to confirm this next week but my doctor said because there was originally a heartbeat and there isnt now I most likely had a missed miscarriage. I’m so sad.