Dear Eric E

mmmm...something is definitely not right...what happens if you carry you baby supported by his belly? is he floppy? by floppy i mean head and shoulders stay drooped or he raises his head up and arms?
does your child know where his mouth is? do you see him trying to put stuff in it?
by 6 months-ish children usually can sit...and they have begun to play in that position putting things in their mouth...
Does your child show any recognision of you...ie...does he smile when he sees you? does he attempt to play with your face?

I am not a peadiatric physiotherapist but your description suggests something is wrong...in the delay of motor and social milestones...

Post this in pediatrics someone would be able to help you there...

my advice, demand to see a pediatrician, perhaps a specialist in Cerebral Palsy and Autism

cheers