Immaculate conception?


I have spent all week wracking my brain over this and feel completely insane. Curious if anyone can help me understand.

LMP 6/29. Assumed ovulation was 7/13. Had sex once and once only on 7/12. Did not have sex again for two weeks. Negative pregnancy test on 7/26 (day before period due), positive pregnancy test on 7/28, which would have been 29th day of cycle (late by one day). Recently got period back after first baby, but last two cycles had been 28 days exactly.

Thought I was 8 weeks 2 days on Monday and had first ultrasound. Dated at 7 weeks 3 days with a beating heart. Was beyond confused by this, because I thought sperm could only live for 5 days. I was having so much anxiety about it that I went today for a private ultrasound. Measured at 8 weeks exactly, which means Monday was also correct.

HOW AM I PREGNANT? Can sperm last over 5 days? Does my husband have super sperm? Nothing makes sense! Even if I ovulated late, which I totally get, there wouldn’t/shouldn’t have been sperm there to fertilize the egg?

Totally happy/excited about this pregnancy, but just so confused. 🙃