Don't worry Freya, we all have those days! Kids know how to press our buttons at the best of times, and the lack of understanding and constantly having to repeat yourself can be frustrating. I've found that if my daughter doesn't seem to be "getting" it, sometimes changing the modulation in my voice can help. When we use cranky voices (which can be REALLY hard not to) ASD kids don't seem to hear the words just the tone. I find that if I talk at the front of my mouth rather than at the back she seems to "hear" me better, but it's not a natural thing for me to talk that way.

Fiona, I really encourage you to do a sensory profile, it sounds like he was either over stimulated or under stimulated. There's a do-it-yourself checklist here. It would still be worth getting an OT to do a proper one at a later stage though, even if it's just to confirm.

Often, for a sensory seeker, sending them to their room to calm down is the opposite of helpful unless they are over stimulated - In that case they need a cave (i.e. sensory deprivation area). Otherwise time in's, where you give them a job that is either tactile or requires heavy lifting, is a much more effective option (i.e. "go out in the back yard and find me three stones, a gum leaf and a yellow flower" - obviously no stones if you think he'll throw them...). It also gives you an opportunity to turn it around from telling off to praise which is more positive for both of you.