Lumps in testicle! Do I have cancer?

I am 15 and about two weeks ago I found some lumps in a softer lump on the top of myleft testicle. As normal I went to the doctors the day after and she said we should wait a few weeks because these things usually dissapear. After a week I couldn't bare the tension, I went to the Emergency section of the hospital because it was a weekend, he said that it was the epididymis and said it was normal, I am not convinced. I have been worrying about it and although the doctor said it was the epididymis the lumps can be moved around the top of the scrotum, there is one bigger lump about the size of a small pea and the others are smaller than that. I'm thinking of going back to the doctors to get a scan, could you giver me any ideas on what these lumps could be? could this be because Im going through puberty? please reply! thanks :-(