Skywalker - We have a 4yr old daughter and have gone through a similar experience to since she was about 14 months old. Our daughter was diagnosed with a genetic condition at 14months after progressing normally from birth until about 8mths when she started to lose her skills. She now has Epilepsy, Breathing problems, has a feeding tube into her stomach, cannot walk or talk and has limited life expectancy.
But, she is still our beautiful little girl, she can communicate with her eyes and when she smiles she lights up the room. Epilepsy is managable these days via a whole range of drugs that do not leave you with a 'monged out' child and the Special School she attends is brilliant at helping her.
Having a child with special needs does mean your life will be different but I have gained so much understanding of children with special needs that I feel I am a better person for it.
Life tends to throw you some curveballs, but the human spirit is a resiliant thing.
Chin up mate, if this forum has shown me one thing is that there are some great people who will rally round when you need it most.