Menstrual abnormalities, could this be serious?

sounds to me like your going through more changes in your life. A woman never has regulated periods until she's at least 18-21...sometimes older...sometimes never. Just when you think you know your body, it laughs at you and changes. There's a huge chance that it's just your body changing more and trying to keep up with your new hormone levels that a teenage girl goes through. Just to ease your mind, I'd talk to your mom about it and schedule an OBGYN appointment so that the dr. can do a more indepth look to make sure there is nothing serious. I know the big "O" dr. is a scary place to think about going, but it's really not all that bad and it doesn't last that long either.