New sleep problem

Hi

I am the mum of a 9yr old with CP (cerebral diplegia). He has slept through the night (unless unwell) since he was 4yrs old. He would always wake up early (around 5-6am) but would sleep until then. For the last 2 months he has been waking in the middle of the night. Around midnight to 2am. He comes to find us (his parents) and says he has not been asleep and he needs help. We know he has been asleep and check on him at least once before we go to bed. His bed routine includes toilet, teeth, bath story and then kiss /cuddle goodnight - this occurs around 8pm. 
We are becoming exhausted as I have health issues too and we both work. When he wakes he wont settle in his own bed and we usually have to take him to the spare room and lie with him to get him sleep again. 
His room hasnt really changed, his bed is comfortable - he picked it and gets off to sleep quickly most evenings. 
He is a very clever boy, and very articulate so I have been trying to ask him what is going on but he doesnt seem to know and is convinced he hasnt slept at all when he comes to us.

Any advice or suggestions as to what might be going on will be gratefully recieved.

He does get occasional migraines but he doesnt describe pain in the night. He doesnt get muscle pains /cramps any more since having SDR in 2011. He does overthink things and a bit of a worrier. 

Hope to hear from you

Thanks
Claire