Missed pill

Jelly

Need some advice, I went back to back with my pill so have been on for about 5 weeks now but I missed a pill recently and am not sure which day it was

I’ve been having fairly regular sex but the guy actually does biology and says I will have been ovulating last week not this week and since I’ve been back to back should be okay

Since I don’t know which day I missed I can’t take the morning after pill but idk what to do

Please give me some advice!