Hi K.-
My nephew gets alot of gas and has a hard time burping (but eventually does). When I burp him, i pat the under side of his bottom while he is propped over my shoulder instead of his back. If I pat his back, I pat the lower back. It seems to soothe him and rustles the gas to one end or the other, sometimes both. =) If you are using bottles that eliminate gas, he may not have much- or if you are breastfeeding and his tummy is compatible with your diet, he may just not have much. Does he spit up at all? That may be where the gas is if he has any. I have noticed that the older they get, the less they burp- one good one and then they are wanting more.
Hope this helps!
-E. M.