Sorry to hear of all this, must've been very scary.
Im not sure of the formula,but Im a huge fan of probiotics. All my babies go on them as newborns. I would not get a commercial brand, but go to a GOOD health food store where there is a natropath on duty, and they will recommend some. The one my DS is on is called lifestart. My kenisiologist prescribed it to him, and then yesterday when I was at a health food store, the natropath confirmed it's a great one for young babies and toddlers.
Hope DS is well soon xo