What Causes Multiple Lumps In The Breast?

Hi, this is a really weird problem I have... I am 26 years old female, my left nipple remains erect all the time, since last two years... I had asked 2 doctors about it, but they didn't have any satisfying answer. My left breast has 12 lumps. So is it some kind of warning?? I would love to have a normal nipple because this one is irritating, painful and embarrassing.... help please