My period keeps coming early and is very irregular?

I'm 16 and I got my period when I think I was 13 and it still hasn't become regular. At first i was getting it only like once or twice a year, and my mom took me to the doctors and they said that it's probably still regulating and stuff. And now it'll skip a few months or maybe just one month, so it seems to be getting regular. But lately I've been getting it really early. Like I've been getting it almost every month now and sometimes I'll start spotting off and on for a whole week and then the next week I'll get my period. So that's been happening. And I was supposed to get my period the day after Christmas, but it came almost 2 weeks early and ended a few days before Christmas eve. So now I'm not supposed to get it until the end of January, but today I noticed a little bit of blood. Why does my period keep coming super early? It just ended last week. I shouldn't have it already! Is it just my period trying to regulate???