Gassy baby

My 4 month old seems to have a build up of gas at night and it's making it hard for him to sleep. We've tried all the conventional tips - burping, moving his legs, gas drops, gripe water only seems to make him more uncomfortable. Nothing seems to help. He has a very regular poop on his first awake bottle of the day but after that it's rare that he let's anything out.

Is there anything else we should try that has worked for anyone?

(We will not be putting anything up his butt, just to rule that out now)