This is hard to post because I truly dont feel like he's behind in the way that there's something wrong with him...but the more I see babies his age sitting unassisted or crawling or almost crawling makes me have a little anxiety in my belly.

T is not sitting. He can support himself in the tripod position for only moments and not always. He can roll to his sides but still hasn't started rolling back to belly yet. I know crawling is a long shot for 6 months, but I know 2 babies his age who are full on crawling and he hasn't even started getting on his knees or anything. He's on his belly and kicks his feet and that's it.

He doesn't like to have tummy time at all. He quickly rolls onto his back. We are persistent but I don't feel like it's enough. DH does "pull ups" with him all the time and we practice sitting. His doctor wants him sitting by his check up on the 22nd and at first I thought that would be no problem but other than establishing a few seconds of tripoding since then, we've had no progress.

He can balance himself well when I hold him upright, just a little shaky. All of his mental development is completely on track, if not ahead.

I don't know what to think. I don't want to be worried, but DH is stressed about him not sitting yet and it's stressing me out!! Seeing other 6 month olds sitting and crawling isn't helping.
What do you bees think?