Help. FTM Here

Hey everyone. So one of my breasts is being strange. I feel pain close to the outer edge of breast towards the armpit. Pain is like a dull ache when I move around however I can’t pin point exact location when I massage my boob. There are no lumps, no engorgement (baby seems to drain breast correctly). It’s not red or warm. All of these things make me think I don’t have a blocked duct or mastitis. However the discomfort is definitely there. I’m still exclusively breast feeding and a first time mum. Does anyone know what might be going on?