MY SON HAS PDD NOS AND SEEMS TO BE GETTING WORSE?

I have a 5 year old son who was dx'd with Pdd-Nos. He was doing really good for a while. But as of the past few months he seems to be getting worse. He has alot more meltdowns, and they last alot longer. Some times its a whole day thing. Its Not predictable anymore what triggers him, Or what will help him. Is it normal for Autistic children to have such extreme ups and downs? Or should I be worried something else may be going on? If you could just share your advice or story I would appreciate it.