Conceived with 8 day old sperm? wtf?

UPDATE- I am now 13 dpo and officially late on my period, and all this has happened. 😂 I have urinary urgency, and had three or four pale brownish/tan mucous spots last night and this morning. it was supee discouraging to see that, because thats exactly how my last two chemicals started. Was sure I was headed for a third chemical pregnancy. well, i tested again today at 5pm with a FRER and a digital, and my lines were still progressing in darkness and now the digi is positive. my lines never progressed with either of ny chemicals. they stayed faint, then i began spotting then bleeding. this time around is different, but i am still cautiously pessimistic until i see baby on US.

Okay, I am completely baffled. Had sex ONE time, January 29th. was doing a cycle study with my OB so she did ultrasounds on me to confirm when I was ovulating. ovulated either fwbruary 5th or 6th, a full 7-8 days past sex. Two positive FRER tests today, with darkening lines. I am 10/11 dpo, based on the transvaginal ultrasound they did. WTF. is this possible? im like... 🤔🤔🤔🤔 i have PCOS. could the ultrasounds have been wrong?