Could I be pregnant?!

My boyfriend and I have been having unprotected sex and he finishes inside me.. my period is late by five days. Usually, when my periods late it's only by a day or two and usually I feel  symptoms of my period coming... I am not getting ANY signs of my period at all. I know I could take a pregnancy test and find out, but has this happened to anyone else before and it was just a really late period??