I am 15 do I have a good change of getting bigger on birth control?

Look at the instert of your pills for side effects it should be able to tell you if enlargment is possible. You have just started the pills so if it is possible, it may take up to a month or more to see the change. Having a hormonal imbalance is probably the reason you have no/little development. And maybe gaining a little weight from the pills could be a good thing. For most women the first place they gain/lose weight is their . I think that once your hormones become steady, you will see some development.