Lump under breast? It moves and it's getting bigger?!?

Okay so I found a limp on my breast that started out small, under my nipple. I am make if that matters. Now it feels like it got bigger, and it goes mobile if I manipulate it... It dust hurt before but now it does if I mess with it. Sometimes I feel very dull pains coming from it, but not that often. Now I can feel it if I barely touch my chest! And it hurts if I do that, too! I have had it now for a couple months. Isis go to the doctor about it, but she didn't really do much. She just felt it and then googled it on her iPad and some medical app. She said it's probably nothing but I'm going to go get a ultra sound sometime next week... But I'm to nervious to wait): I'm 14 if that matters.