I'm starting to think my 4 year old may have ADHD/ADD does anyone have any experience with this and could shed some light please?

I'll start with saying I've done my research.It also runs in the family (my autistic brother has it, so does my son's dad's brother. Then there's, ocd, torrettes and trichotillomania in the immediate family including myself)He has a severe temper, he's drawn blood on myself and my partner on countless occasions, he throws things and kicks and screams for hours. When he's calmed down he cries that he doesn't want to be naughty (not a word we use but a word he's learnt) and that he loves mummy and his family.He won't sit and eat dinner, he'll have a mouthful then run around and so on and so on.He's always fidgeting. Always squirming.I have a lot of hospital appointments and he will instantly start running and climbing, he has no worry about any authority, nurses Dr's etx telling him to stop.He has no fear, and he has absolutely no fear of strangers and this has been the case his whole life. When he was 1/2 I could walk up to a stranger, hand him over and walk away and he'd never cry (in theory)It takes till past 10pm each evening to get him to sleep, even though bedtime starts at 8pm.It's been a long long long time since I can remember him being easy to deal with, we try positive reinforcement, praising his good behaviour, he gets disciplined for his bad behaviour with time outs. But his temper, pushing, kicking, scratching and hitting is getting impossible to deal with and I don't know how else to approach it.I'm just hoping someone can relate and help with any advice? via /r/Parenting https://ift.tt/2T7Xl8q