If I have sex on the first day of my ovulation week that only last 6 days and my strongest|best bd day is the 4th day of that week is it a possibility the sperm will be strong enough to last the whole week and still end up pregnant or does it all depend on the sperms life span?

Any stories of having sex only one day and going on to get a bfp?

My husband and I will be very busy, my fertile week started in the 30th, was told January 3rd is the best day to bd but we might not be able to get it in that day so I'm basically going to be relying on December 30ths little swimmers this month. Last time around we did it only on the last day of my fertile week around midnight and that worked |it ended in miscarriage, but it kind of gives me hope, only it's backwards so not too much hope| thanks in advance and happy New Year.