Having sex for a week and light bleeding two days before period,period lasted about 8 days

I have had unprotected sex with my boyfriend using the "pull-out" method, and i began to bleed very very lightly two days before my period was supposed to start. Then the bleeding got a little heavier. This is the only irregular cycle I've ever had. Now I was getting light cramps for about a week or two after my period. What could this mean, could I be pregnant?