So My Boyfriend And I Had Unprotected Sex 5 Days

So my boyfriend and I had unprotected sex 5 days before I was supposed to start my period, he didn't ejaculate inside me and I was one day late and when I did start it was a brownish color and very light and over the next day or two it got a bit darker and a tiny bit heavier. It was unusual because my period is normally 7/8 days long and this one was 3 days. What could have caused this? Are these signs of pregnancy?