Fiancé thinks I need Plan B

Last night my fiancé and I had a little bit too much to drink and ended up having unprotected sex. I was not on BC at the time (just started today - I had planned to a few weeks ago) but it was CD 2 for me. My cycles have been 24 days on avg the past couple months, which would put ovulation somewhere around CD 10 for me. This is consistent with the EWCM that I’ve observed around the same time. My fiancé thought I should take Plan B but I explained to him where I’m at in my cycle and that sperm can only survive up to 5 days. I feel like I’m probably okay given that I would have to ovulate very early as well as a lengthier survival time for sperm. These two occurrences seem pretty rare. I’ve taken Plan B in the past and it made me feel awful so I’d rather not do that again if I don’t need to. Constructive opinions?