random bleeding?

so my period isn't due for another 12 days, what would be causes for me to have slight cramps (very very very minor) and be bleeding? it's not heavy at all, very light. 
I did have sex on the 25th of Jan, if that counts for anything:/ it was unprotected but he pulled out, I know there's still a chance for me to get pregnant so thats why I'm worried...