For 4 months i've had a swelling in my armpit by my left breast which is painful at times and it sometimes makes my whole left breast hurt. i seen a doctor but he said it was nothing to worry about. ?

Second opinion?: While there are a number of possibilities here, swelling in the armpit may represent an enlarged lymph node. If you have recently nursed a baby, you may have an infection, e.g. mastitis - though this usually presents with a fever. While breast cancer doesn't usually start with pain, I'd want to rule this out - though it is unlikely. Good doctors value second opinions. Make sure you're comfortable.