Ok I am 17 years old of age, my gf is 16. well anyways me and my gf had sex for the first time and i had protection on which is a condom,.it was around between the end of october & november i am not really sure. but from there that is when everything has changed,. which i mean when i had protected sex for the first time, her period changed and she still hasn't got it, she did a pregnancy test and came out negative. but from there we had sex for a couple of times now and they were with condom,. but then from there, couple weeks ago, we had sex and i had a condom, then from there the second sex activity i didn't have any so i did it with no protection,. but i did not finish in her or ejaculate in her,. and at that time she still hasn't had her period yet. then our last sex we had was on the december 1st which is on a saturday in the morning unprotected, and went in her really deep, roughly as you can say, is this why its causing her period to come late? i am really worried, 2 months late not having her period yet? is it because she is stressed out a lot? she has told me she is stressed out a lot. but I'm just not sure anymore,. someone help me out please? i don't know what to think anymore