Confused

Okay so I'm 16, and I've had unprotected sex 6 times in the past 3 days with my boyfriend (please don't judge me). We also had unprotected sex a month or so ago. I wasn't a virgin before this, so I know it's not my hymen breaking, but when I got home I found there was a little bit of blood in my underwear.  I'm not supposed to be on my period for another two and a half weeks. Any idea why I might be bleeding?