There is no way that you can naturally enhance your breast size except for pregnancy and that is never a good idea just to get beiiger boobs. I am lucky I am a 36 E and 15 years old naturally, anyway if you really want to enhance your breasts then there is a bra called the boob job bra which you can get from Ann Summers but you will have to get another adults to purchase that for you. This is not push up bra, it is shaped specifically to mould the shape of your breasts in the best way so they look significantly bigger.
You are 14 years old why do you want to enhance your breasts anyway, you should not need them bigger, be happy with what you've got, many people want to downsize because their breasts are so large that it hinders their breathing and gives back problems. Just be happy with what you have and concentrate on your studies and being a happy teenager. :-)