One of my breats is significantly smaller than the other one. One is like a C cup and the other is like a cup. They have been like this for a year now. One keeps growing. The other doesn't. Should I see a doctor?

It happens... and it does happen more frequently than you think. THere really isn't a lot that can be done before they stop growing and you can either get a reduction in the large one or a augmentation in the smaller one to bring them closer together.

It's a fallacy if anyone actually believes both breasts are the same size in most women, they aren't, they might be fairly close in most but there is always a variation and in certain cases it can be obvious such as yours.

I actually know someone who's daughter had this same problem when she was growing up. You aren't alone, in the meantime you can use a prostetic or padding in the smaller cup to make it more comforatable for you. Unfortunately its not practical to do much before you stop growing because it would likely need repeated in a fairly short time. And maybe you will get lucky and the one will catch up with the other in a few more years.

I'm assuming you are in your mid teens... if you are already in your early 20's. Perhaps its time to speak with a doctor about your options.

This is very true, really no women is the same, and all body parts are never exactly the same.

I know women that have to use padding to keep the same appearance.
But often in teens, the difference is more noticed.

Of course, talking with your doctor is never a bad idea. To be sure there is not other issues.