I want to lose 2 stone?

Im 13, around 5ft 6 and 11 1/4 stone. I have a bulge, but i CAN see my feet :L But also I have problems with my legs, so running isn't as easy as it sounds :L I can still exercise, i just have to be careful, if you get my gist :P Is their like any herbal remedy's that you can buy at local supermarkets? Nothing illegal, obviously, just something....... that works :L