We have gone through many different kinds of formula - even the expensive prescription formula (Elecare, $80/can). The docs all told us to give it at least 5 days before switching... and only switch with the doc's advice on what to do next... what to try next.
Call your doc if you're concerned about the # of bm's/per day he's having, but I think 6 for an infant is fine. If there's blood in the stool, then there's a concern for that. Or if the baby is constipated for like 2 days, then that's another reason to switch formulas.
Is your baby fussing during feedings - is that how you know he's gassy?
I only ask because for weeks we thought my daughter was majorly gassy, but we've come to find out (after an xray swallow study) that she has problems with her swallow coordination and we had to thicken her formula with a thickening agent (it's the consistency of syrup or honey)... and that has helped tremendously! She no longer acts like she's gassy/fussy. Let me know if you have more problems and the formula doesn't solve it ... you might need to see a pediatric GI doctor.