Sore side of boob/under the arm

[krystals]

Hi lovelies
Bubs and I are having a terrific BFing journey- all is working well feeding wise. Just wondering if any of you have experienced soreness in your boob near your armpit? It's not hot, and there are no lumps... but it's quite sore, starting to radiate, even when I lift my arm.

I'm not sure if it's something to do with my boob, or the fact that DS just went into a harness, so I'm lifting him differently. He's still feeding really well on that side- but is this what mastitis feels like?

TIA
K

PS- he's feeding MORE at the moment, not less