Any suggestions????

We have been working on tummy time with Brayden for quite sometime. At first I was concerned he wasn't lifting his head when he turned 3 months, but after hours of watching him, that is not the problem! Brayden cannot figure out to use his hands while on his tummy!!! He can sit in his bumbo, sit when I hold him up, pushes off my shoulder to sit up, and on his tummy he lifts his head, turns it all over the place, looks up and around at what's going on, but gets easily frustrated because he wants to life it more! My poor baby! We have tried holding his bottom down because he seems to be trying to use his legs not arms, and we have tried placing his arms in a push up position and holding them. None of these worked. We have also placed his arms under him so he has to move them and use them to get up. Nope...not working either. Any suggestions to help me get him using his arms!!! I know he is aware of them because he is eating them all day long!!!