Large irregular lumps in both breast

I am now 17 and since I developed breast I have always had these big lumps in both my breast that feel like irregular shaped rocks. I always thought it was normal until I was 15 when I was told it wasn't. I decided to go the to doctors at 15 and they said I'm ok and that it should go away as I get older. Two years later and I still feel no change. They are still there and the same size. There is at least one big lump in each breast that feels like it takes about half the capacity of the breast. There are also a few really small ones in both breast. I just recently realized that the lump in my left breast is a bit larger then the one in my right and now I can see that my left breast is noticeably larger then my right.

I am mostly curious if anyone else has this and if they can tell me more about it. I've never heard of anyone else having this and it honestly freaks me out a little.