hi again lets see if this helps you so your cycle day 1 first day of your period day 14 give or take a day is ovulation day now you guys sperm needs to be in place for this and it takes 3 days for it to get there after unprotected sex and once its there can live for around 7 days but its best if you have sex around day 9 the sperm splits up some goes the left ovary and some to the right so out pops you egg and away you go hopefully to pregnancy if on day 21 you get spotting its because its implantation day the day the egg implants itself into the womb lining. so after this if you miss your period then you do an hpt or see your doctor for a test. do hope this helps you. good luck ps that's why i did say just see why now unknowing your timing was right just.
we had intercourse the 17th and 21st and ovulated the 21st when did i get pregnant