Confused

I had my first ultrasound yesterday I thought I was 8+1 baby was measuring 6+2 they couldn't find the heartbeat but they said it could just be to early but to go back next week and they will tell me if I had a missed miscarriage. My husband thinks we should get a second opinion if they still can't find a heartbeat next time. I just don't know what to think. Is it possible I ovulated two weeks later than I thought I did? I wasn't doing ovulation testing or planning on getting pregnant we just happened to have unprotected sex twice last month.