Missing Milestones?

Katie
So my guy came on August 9th- he'll be 4 months a week from tomorrow. He grins like a fool and makes lots of noises back at you when you talk to him, and his head control seems to be really excellent when we're holding him. However, he is not yet reaching for things and he hates tummy time so much that he won't even try to lift up his head. He just face plants after about 10 seconds of looking around and screams until you pick him up. 
 We've tried a bunch of stuff- shiny toys, noisy toys, brightly colored toys, even dangling his binky in front of his face, and he'll stare at them all day and he flaps his arms when he's excited/happy, but no attempts to actually grab anything. For tummy time we've tried getting face to face, putting a mirror in front of him, putting towels or a boppy under him.... I'm out of ideas. Right now we're trying to have him spend a lot of time "standing" or sitting up in his bumbo seat and hoping that makes up for the abysmal tummy time. 😖
Where are your munchkins at- anybody else not reaching/grabbing or lifting heads up? Ideas????
Edit to add - he came 9 days early via emergency c section but as soon as he was out he was totally fine, and I wouldnt think that's early enough to need to adjust development timelines like with preemies....