first, take a deep breath and relax.
i have a daughter who is now 21. she, like you, was thinner and "top heavy"...
as you age into your late teens and 20's you will find your curves change, especially your hips.
change doesnt mean fatter... change means you will find better proportions. at 15 my daughter was busty and skinny. at 21 shes womanly and has curves.
in the meantime there are things you can do. some bras offer more compression. if you are that big you dont need extra padding unless its an issue of "poking though".
exercise is important. you can also better define your chest musculature with weights.
the honest answer is you, like the teen boys whose feet are still too big for their frame, are still growing. you arent set in stone. your body is very likely to change form.
and honestly... the girls with straight hair want curly, and the girls with curly want straight. you have curves now you arent ready to deal with... partly because girls can get b!tchy about it and boys are just idiots about it.
breathe in and breathe out.
my daughter demanded breast reduction at 16. nope. nada. no way.
now, at 21, shes better proportioned, and glad we didnt listen to her real, honest frustrations.