It's probably just spotting l,but if you are concerned jjst to be sad got to your doctor and ask, better safe than sorry
Since you're so young it could have been that you got a period, and now you're not. In the beginning it is common for it to be irregular.
Do you feel OK? Do you have any other symptoms? Probably not... If no, then it could be just that. And you don't have anything to worry about.