Help!! Gassy baby

I have a lot of troubles getting my baby to sleep. When I put him on his crib, 2-3 hour later he starts to make little complain noises and puts his legs up like trying to poop or pass gas. Sometimes a fart comes out and he stays calm for a while but it is always gas that wakes him up with pain.

I feel thats not letting him sleep :(

My question is: if he is sleeping well for 2-3 hours and all of the sudden he is gassy. Where does this gas comes from if he is sleeping??! Im not sure if this is a normal thing.

My pediatrician says it is emotional and that my baby wants to be held like most of the babies. But I dont think that is because he is ok sleeping on his crib for a couple of hours until something in his stomach upsets him😭😭 heeelp