Baby Not Burping?

I'm having a hard time getting my 1 month old to burp after breast feedings. I try different positions (on his side, over shoulder, on my chest, sitting upright on my knees), I'm lucky if I get one out of him! I try to keep him upright for a while afterwards too, but even a while after that he'll spit up a bit. Not a ton, doesn't seem to bother him. Any advice on getting burps out of him easier?