my beautiful son

I have a three year old son, he has learning difficulties (special needs) as they call it now.He is delayed in many ways and has been under a childs consultant for the last two years. my biggest concern with him though is that he always stiffens up,  its like he has no controll of what he is doing, he is also very clumsy and can not walk far. My son has had many tests, including an mri scan but all came back clear, i have expressed my concerns to his consultant at every review but she just sort of shrugs it off. I no that this is not normal because he is even doing the moovements in his sleep, he just carnt keep still.  he has started nursery there is other people telling his consultant that this is happening too, like his teacher, special needs teacher and they also expressed that he scares the other children due to his uncontrolled moovements. He is such a loving child, so friendly and sociable and he is going to find it hard when starts school, i just dont want him to be singled out. was just woundered if any one had any advice for me,  Im not looking to change my son,  I have also menchaned on several occasions to his consultant that when i was pregnant, two weeks over due my waters broke, they took me for a scan to confirm this then sent me home for a week cos there was not enough beds left, so one day somebody menchaned that my son being the way he is could have something to do with my waters and inffection, could this be true? thank you for taking the time to read this and sorry about the spelling.