Try to leave baby laying down for a while after feeding him... Like assuming you hold him while feeding him try leaving him on his back about 5 mins.... Then pick him up and try to burp him thats what i do with my baby

I massage his back sit him up like a frog, move him around. and it still takes forever so idk if it is his formula @mommybump2016

Hold him up like if your picking him up from laying down, so his body moves. I don't know how to explain it that well but after than sit him in your lap, hold his chin and burp that way.