Gas, switching formula?

Hello Everyone!

My LO has painful gas that keeps him up at night (and very unhappy during the day). We started on Similac Advance and switched to Similac Sensitive Pro. There was a little bit of improvement but it's still pretty bad. We tried the gas drops and they seem to work some at first but again didn't solve the problem. We were thinking about trying Enfamil Gentlease. Has anyone found any solution to cure the painful gas? Also, if you switched formulas, how did you make the switch, did you introduce slowly or all at once? Thank you!