Found a lump.. What should I do?

I'm only fifteen years old, and I found a lump in my breast. I have a family history of cancer (breast, skin, liver, heart, etc.) but I don't want to overreact. I first noticed it about two months ago.. What should I do? I know that breast cancer is extremely rare in teen girls, but I have had quite a few strange health problems, like a rare type of hernia, asthma that doesn't respond to meds, and many other unexplainable ailments. I'd rather not see a doctor, because I'm quite sure it's nothing to worry about. Still, I don't want to take any chances. Any advice is appreciated, thanks.