B.W.
I would recommend you stop switching formula's! Spitting up, fussiness, and gas are all COMMON IN ALL BABIES! As is moving between runny and firm bowels. Not a reason to flip through formula's. It takes up to two weeks for a child to get used to a new food, especially infants with baby formula, which is hard to digest, and will cause intermittent loose bowels, then firm bowels, as the child passes things in the formula his body can't use.
Stay with one formula, you are causing way more problems switching to different formula all the time. The problems you listed are what babies do, they get gassy, they get fussy, they spit up, they have intermittent bowels. Its not cause for alarm, stick to one food for him.