Is it normal do have my period every 1 and a half - 2 weeks?

Im 14 and had my period in late december. Then I had it a month later in January and then a month later in February. Except, ever since February I have had my period like 4 or 5 times as I am getting it every 1 -2 weeks. This is really frustrating as I do alot of sport (netball, athletics, touch) and it kinda affects my sport. I asked my Mum and she said she isnt sure so yeah. HELPP!