My 10 year old son wont sleep, Advice?

My ten year old son has autism and he is usually a very very good sleeper but the past two days he cant sleep for the life of him. I am not sure what to do with him. Because when he dose not sleep he tends to have allot more meltdowns then when he has slept. And that's the problem he has been super irritable and moody and have allot of meltdowns. HELP!!!!!!!