Small red patches on my breast?

I have periodically noticed that I get these small red patches on my breast (usually on the right). They're not too dark but definitely noticeably redder than the rest of my skin. they are a little less than a centimeter in diameter, and right now there are about 4. They feel slightly raised but that could just be because i put lotion on to try and help. I am wondering if it has something to do with the weather change? I jog somewhat frequently and I have been sweating alot more. Also, I am about a week away from my period so my breasts have been swolllen. The red patches come and go..sometimes I noticed them really easily and sometimes I can barely see them. Any suggestions? It's starting to make me nervous. Oh and I'm 19 if that helps.
Thanks!