Switching Formula Advice?

Danielle
Looking for any experience on trying different formulas. We're exclusively on Enfamil (ready made liquid) but my 7 week old looks so uncomfortable at points during his feed, I'm kinda wanting to try something else. Digestion-wise, everything seems to be passing through okay and he rarely seems gassy to the point of discomfort so I've been hesitant to really mess with his system, but he's a grunting, straining, animated mess 1.5-2 ounces into every feed. 
Do I just make a cold turkey switch to something else or should I try easing him into another formula? I have his 2 month appointment on Monday and will be discussing with his pediatrician then but would like to see if it's an issue with the formula before then. Would love to hear if anyone has experience with this!