Hi mamas! I hope you're all staying healthy and safe!

My little man in 5.5 months old, and I'm concerned about him inability/disinterest in sitting up. He can roll both ways, but whenever I try to practice sitting up with him, he almost acts as if it's uncomfortable or hurting him 😢. Additionally, if he sits up too long he typically spits up, which makes me think it's hurting his belly.

Anyone else experiencing this? He is pretty chunky so maybe that's the issue?