Hi, welcome to HCm, I am Dr. Das
First of all, you have a very regular cycle.
Normally, ovulation occurs on 14th day from the first day of last period. But 10th-18 th days period is taken as a fertile period.
So, calculating from the first day of last period you can easily identify your fertile days.
And one more thing , pregnancy
test should be done on the day of missed period.