Pain in right breast????

I'm 19, never been pregnant, not sexual active, etc. for like a week, I've been having this aching pain in my right breast mostly at the side and near my armpit. I've tried massaging it but it didn't help. It hurts to sleep and I can't sleep comfortably because I usually sleep on my side or my stomach. does anyone know what this might be? I don't feel any lumps btw.