Concerned about a non-viable pregnancy

I am an L&D nurse. My husband and I stopped birth control in July, I had an ovulation tracker app and what I thought was my period was 4 days late with 2 negative tests when I was "late" I have not been off BC in years so I'm just hoping I ovulated 9 days later than what the tracker says I should have.  I wasn't convinced I was not pregnant the other day and got a BFP. A coworker and I played around on the ultrasound machine when I thought I was 6 weeks and 3 days. All we saw was an empty gestational sac and it measured 5 weeks and 1 day. I know too much and am afraid I'm correct on my dates and could be experiencing a blighted ovum. Did you ovulate late after stopping birth control and get a BFP the first month? I don't have an official ultrasound until the 30th and am worrying myself sick.