You have a point that it could just be learned helplessness. Needless to say you probably want to get him on his feet and walking and talking soon. What does your pediatrician say? I would talk to them first, but I am a special education teacher, and what a lot of parents don't realize is that you are entitled for the disrtict to pay for services from the moment your child is born. They would rather intervene early and get a problem resolved than wait until later. If your doctor has some concerns, than contact your local special education parent teacher association and see what can be done. Probably an evaluation has to take place first, and they would determine if their is in fact a problem. If there is they would start him on some type of therapy... again that is covered by the district. If the district blows you off (which they have a tendancy to do), be the squeaky wheel. No other place more does the squeaky wheel get the oil than with special education.
Good luck, I hope everything turns out okay.