Uncomfortable baby?

I have a 3 week old who is drinking a combination of breast milk and formula. Sometimes after he eats he seems either uncomfortable, not satisfied or gassy and trying to poop. If I try feeding him more he takes the bottle with no problem... which makes me think that he is still just hungry....spits up very little ( especially if he is trying to poop right after eating) I feel like he may have silent reflux? What are the symptoms of that? Him seeming uncomfortable doesn’t last for long, but it just concerns me. Can babies have silent reflux this early? If he takes a bottle when he is doing that could he still just be hungry?

It only happens right after I give him a bottle and then he falls asleep and will sleep just fine.