How likely is it for a girl to get pregnant 2-3 weeks before her period that month, we had protection but we rant 100% sure if it broke or not.

Fertile time: Studies suggest that pregnancy rate can be about 2.5 % for one episode of intercourse by a random male with a random female, but odds increase up to 80% if male is fertile and woman is at ovulation time. There are many infertile couples, some related to low sperm counts, and some women not ovulating even though they have regular periods. If a small risk of pregnancy is unacceptable, use Plan B.