2 1/2 year old MRI results were a large amount of white spots, I was told this is why he has a major speech and motor skill delay. Is this true?

More than likely. It is! if you are not sure or not ready to accept it, get a second opinion. Hard to say without details of your child's medical history. What is the diagnosis? Was he premie? Any defects in the chromosomes etc?Please sit down and talk to your pediatrician or neurologist treating your child to understand it better.