Gosh megs, my heart goes out to him and to you as a 'helpless' mum. I was diagnosed properly with migraines when i was 9, but had been suffering for maybe a year or so earlier. I'm sure it's much much easier to deal with in an older child. But that's exactly what would happen to me - headache, fuzzy eyes etc, vomit, sleep, wake up better. I had an MRI and a cat scan and a few other tests on my eyes etc to rule out possible other nasties that could be causing it.
Stuffy conditions, over-exciting occasions, very strong smells, stress, the list of triggers goes on.
We did keep a food diary for about 6 months too, to rule out foods and food combinations.
I would seek a doctors opinion.

Good luck with getting an answer which leads to an improvement in your DS's health.