Confused

So last week I went for a scan and they saw 2 sacs, one was empty but 1 had a baby. The tech said I measured at 5.6 days, baby’s HR was 95 bpm. Today I go in for another scan to check the second sac again and it’s empty, so 1 baby, I’m okay with that. But this tech said I measured at 6 weeks exact and baby’s HR is still in the 90s. The doctor scared me and said to not be surprised if I miscarry again, I miscarried on 3/14/19 at 7 weeks. So my question is has anybody been through this situation and baby came out fine and strong. I go again next week to measure baby and HR.