Is my baby behind?

Bekah

I'm worried my 4 month old is behind on almost everything :( hes rolled a couple time belly to back, does basically crunched trying to sit up and has jerky but strong head control when sitting. But he will NOT go up on elbows during tummy time, his feet are never flat standing and he doesnt scoot anywhere on his back??? Does grab at anything but his bottle...He was born at 34 weeks but i never realized he could be behind like this or is it just me?