I Am An 18 Year Old Female, And About 5

I am an 18 year old female, and about 5 months ago I was getting into the shower and noticed a small red dot on my left breast. There was no pain or lump, just flat. I shrugged it off and it eventually faded but it left a little mark. About 2 months ago, I began getting a few more, and these flat red dots are on both of my breasts now. Still no pain or lump and no physical changes in my breasts. What could this be? I am worried now since more have appeared.