N.B.
Stick to a formula longer than a few days to find which one he tolerates. (You've switched 3 times in less than 2 weeks---that's too much.) Excessive gas and spitting up may be caused by not enough burping. Wet breathing can be the result of aspirating vomit or formula, or just him trying to breathe and swallow at the same time. (The Dr. needs to listen to his chest if he seems to have trouble.) Very young babies need to be burped every ounce or couple of minutes until they learn to suck more efficiently. This may be the only problem. Burp, burp, and burp again. You'll get to the point where you can feel his tummy and tell if he's got more air in there. Good luck, and it's no one's business why you're not breastfeeding, so don't accept that guilt.