Why might i be bleeding from my vagina when its not my period?

I usualy dont have my period for another 10 days. I just had it a couple weeks ago. Im 14, and iv heard that periods can be iregular at first, but i'v been having mine for a long time now, and they seem pretty regular. To be compleatly honest, it happenede while i was masturbating. im thinking that might have somthing to do with it. i have never had sex, so its definetly not and std. I also read that it somtimes happens when people have rough sex. could that happen with masturbating too? Im pretty worried, so any advice would be apriciated.