Probably due to milk, are you pregnant?
I would call your ob, or go to L&d to make sure your not engorged..
But definitely sounds like you might be.
You can also try breast stimulation to get some milk flow and release the pressure
Its not all.of my breast its just the outer side of.my left breast
Ive put a hot water bottle on it and its eased it slightly but still very painful
Could be mastitis I would get to your gp to get checked out x
Whats that ive never heard of it. Im a ftm
It's an infection in the milk ducts! Can be serious if left Untreated, but also could just be your milk coming in on one side :) best to get it checked though :) x