Smelly Armpit

My son is a month old and I give him a bath every other day to help him sleep better and my breast milk sprays all over he pees in his hair so we bath him a lot. Well his armpit smells like death it gets raw and smelly and looks painful I dry it good after his baths but it keeps coming back. I think it causes him pain and that's why when he's awake he fussed a lot. I feel so bad but don't know what to do. Has any one else's baby's have or had this?