10yr old 'not right' but bloods ok?

[Mamabear14]

I have 10yr old DS who is autistic and has ADHD too. He is ever so thin so I've taken him off his meds and he's eating really well. Though he's only put on a kilo since Feb. Recently he has been lethargic in the evenings. Normally he takes melatonin to sleep but he's been falling asleep before his bedtime with no meds.
He had a full blood count and his thyroid tested last week which came back 'satisfactory' but he's not right and I'm not happy that he's ok.
What do I say to the doc? What test do I ask for? I don't want him to think I'm being silly but I know my son and how he normally is.

Urine dip test for type 1 diabetes?

Was he tested for vitamin/iron deficiences too? How is his mental health, as anxiety/stress/depression can all cause these kinds of symptoms too.

He was yeah, he is so pale you'd immediately think of iron deficiency but it was fine.
His mental health is actually the best it's been in a couple of years, he's doing really well at the moment thankfully.
I will ask about the urine dip too.