Baby drinking less formula...

Hi moms! So my LO is almost 11 months and he's been drinking less and less formula.. he's never been able to drink more than 5-6oz maybe ever since he was born. I've given him 5-6 oz and he never finishes it and refuses it. Nowadays he still drinks 4 oz every 2-3 or more hours but I've noticed he's not finishing his bottles anymore.. which means he's only drinking maybe 2-3 oz every 2-3 or more hours.. I'm just concerned he might not be getting enough formula a day? But when I try to give him his bottle again he refuses and cries or pushes it away.. meaning he doesn't want any.. he eats pretty much what I eat food wise but even then it's very small portions.. I don't think that should fill him up so much that he doesn't want his formula??? What can I do?? Is this normal? Is it because he's eating more solids now? Should I be concerned??