C.M.
Try Hyland's teething tablets for him, you can get them at just bout any drug store or Meijers. I would actually try like an ounce of formula and the rest breastmilk then slightly increase it over a period of a few days. He is getting old enough I would talk to my peditrician about whole milk or goats milk and a solid food diet. I know they are not supposed to go on whole milk until a year old, but with the difficulties you are having I would talk to the dr.