So confused help.

So I’ll be 8 weeks tomorrow. They told me my conception date is March 30th. However It doesn’t make sense. I had sex the 25th, and the 30th I did have sex, however he wore a condom and didn’t finish. He stuck it in for only a few seconds.

Could it be from the 25th but implantation hadn’t happened till the 30th?

It doesn’t really matter, but I’m just confused lol.