My period is 10 days late, but i spot when i have sex?

I have had no signs of my period, no cramping or anything. But when me and my boyfriend have sex unprotected (we are in our 20's) there is some blood on him and a little comes out of me. I'll go to the bathroom and put a tampon in, but the next morning when i check it, theres no blood on it. Sometimes with a day and a half i may spot a verryy small section of the tampon. Why am i not getting my period but spot when having sex? Possibility of being pregnant?