My bladder keeps acting up?

i find it really difficult to control my bladder! like when i need to pee, i NEED TO pee! it can never be the case of holding it in until i can find a restroom, it feels like i'm on the brink of wetting myself! i also have a habit of trying to "hold it in" when i need to go? have i damaged my bladder? is it just weak? there's no pain, no blood, im not ually active, im only 15 years old... can anyone help? thanks :)