Teacher Frustration

I teach second grade and have a student this year that I'm very concerned about. This little boy is very awkward/shaky with all movements. Even his voice is shaky. I have had him in my class for 6 months now and I only see him getting worse. His writing is very shaky, he has a very difficult time holding scissors, always seems off balance when he walks or runs, does different movements with his hands, etc.
I have voiced my concerns to his mother, who keeps telling me that the doctor said everything was fine with him when she took him in last year for his check up. I have asked her on MANY occassions to please take him back to the doctor to have another check up. I don't see how any doctor would look at him and say nothing was wrong!
I even had our occupational therapist come in to observe him and only after sitting there watching him for a few minutes she said it looked like signs of cerebral palsy.
I don't know what to do about it? It's so frustrating when I know this sweet boy needs help and seems to be getting worse!
Any advice? The only thing I can think to do now is have our occupational therapist call the mom to tell her she does need to be concerned and get him checked out. Maybe that will knock some sense into her!