My little guy is 2 weeks old today. He's been on formula for about 10 days, it started out fine but now he gets quite gassy and fussy after he eats. We feed him upright and burp after every ounce, and been using Gripe water and oval before feedings. But he's trying to sleep and seems to wake up in pain crying. Is this worth a formula change? And what to change to?? I'm currently using Enfamil A+ (the yellow box). And if I came how long till I should see a difference?? Thanks for any advice!