help!!!

so like about a week and a half ago, my bf and i tried to have sex. he put on a condom and didn't even put it all the way in, but we stopped bc it wasn't a good time. we did other stuff and i made sure that no semen or anything got around my area. my period was supposed to start on the 20th and it never came...

i tested negative for pregnancy yesterday, and i've been super stressed and have been exercising lately.

is it normal for my regular period to not come this cycle even when i tested negative for pregnancy?