Welcome to HCM.
You have missed period and lastly got at the end of the month for three days.
There are several reason of delayed or missed period. Need to investigate properly.
You can exclude pregnancy
by doing blood test
or confirmed by USG lower abdomen.
A woman may get pregnant from pre-cum,if intercourse is done around ovulation time. So be careful of that.though chances are minimal.
Check test results and consult with your doctor.
Practice safe sex
in future. Be well.