Well I'm hoping you're feeling a lot better now Sins!!... but just in case someone else comes in looking for cures......
mastitis is not fun... the current midwifery approach is hit it hard with antibiotics and keep feeding, (although the milk tastes different and the babies don't usually like it!! + it's agony for the mum!!)
but since you're not nursing.... cabbage is the way to go.... someone up above said "leave them on all day".... I disagree.....
what you should do is put the cabbage in the fridge (cool leaves work better) get the biggest leaves you can but rip the big thick veiny bit out of the middle.... (that is damned uncomfy against an already sore breast).....wrap as many as you can around the breast...
once those leaves warm up and you start smelling like warm cabbage.... swap them for some cool leaves... you can put the others back in the fridge and reuse them later.....