Can anyone give me peace of mind?

Emily • isla’s mama💕

LMP started on June 24th, and according to glow my fertile window was between July 7th and July 12th with July 11th being ovulation day. I had very fertile CM on July 11th and that was the last day we had sex until after I got my BFP on July 22nd (11dpo). So yesterday was our first prenatal appointment with an ultrasound. According to my LMP, I was suppose to be 6wk3d but the gestational sac was only measuring about 4-5wks meaning it was empty. I go back in one week to check for growth. My doctor said then we would know if this was a viable pregnancy. That term just sounds so harsh and clinical. He thinks maybe I just ovulated late, but I feel like that’s impossible since I know the last day we had sex. And if that’s impossible then I feel like it’s going to be empty again next week. I am still getting strong BFPs and I have tender nipples and occasional nausea. I’m just completely terrified and emotionally exhausted. Has this ever happened to anyone? I’d like to hear your thoughts and experiences whether the outcome was good or bad.