What Causes Spotting After The Intercourse?

Okay i'm wandering if you could maybe help me out and tell me whats going on. I had a somewhat heavy period with bad cramping then 2 days later i had unprotected sex and then the next day after unprotected sex that night i had spotting and also the fallowing day what does this mean ? could I be pregnant or am i just spotting normaly ? my period are very irregular as well