Without more info, all forum readers can probably say is:
If your Jacksons is sleeping all the time and grey, then yes, he is sick and needs to go to the vet now if you don't want him to die.
Chameleons can be delicate, and they can die very quickly after starting to look sick.
Look at the permanent posts at the top of the "Health Clinic" form for "How to Ask for Help" and copy the questions and provide detailed answers. The more experienced members might be able to help you improve something you are doing to prevent him from getting sick again after a vet has seen him.
Best of luck for your little guy.