Aiyo, I feel you lah, breast ruam is really uncomfortable, especially bila kena friction from bra! Honestly a few of us mums faced this, and usually it's either heat + sweat, or the bra material itself causing irritation (some bras memang tidak breathable). Try going bra-less at home bila possible, switch to cotton bras yang loose-fitting, and keep the area dry, pat don't rub. Kalau it's getting worse or infected-looking (dengan pus or extreme redness), better check with your doctor atau gynae just to be sure, because sometimes it bisa jadi fungal infection which needs proper treatment.