Neurodiversity or just 4yo behaviour?

[bakingmummy21]

DS 4yr 3mo is just so difficult behaviour-wise and has been for at least 2 years. I was really hoping turning 4 would be a turning point but it hasn’t so far.
We have 3 DC and he is the middle child. I feel terrible saying this but his behaviour is often just ruining our family time. My eldest DD6 has to put up with him screaming and having tantrums and sometimes he will hit her or upset her. He gets incredibly angry about things and will hit or throw stuff around.
Everything seems to set him off and he is constantly moaning and whining about everything even when we’re doing something nice! It’s like he manages to find reason to whine no matter what.
He also has a real issue with my DH, won’t let him do anything, says he doesn’t like daddy. This has been ongoing since he turned 2 and takes a real toll on both of us. DH is fed up of being rejected despite his best efforts and I am fed up of having to do everything for DS.
We have recently completed the ASQ questionnaires with the HV and on the social and emotional one he scored 105 which has resulted in a referral but at the same time I recognise the questionnaire is subjective - and I do hear lots of similar stories about other 4yo’s and that it’s a tricky age. His preschool haven’t flagged any concerns, just commented that he is full of energy.
Sometimes I feel like I can’t imagine him being any other way than he is now and it is so draining. It impacts what we can do as a family and I feel like my DD is missing out. DS hates me going out without him and so it’s hard to get 1:1 time with her. I’m desperately hoping that it’s just a phase but I don’t want to ignore the possibility that it might not be - just feel so sad that his behaviour impacts our other DC and this might be a longer term situation. Any experiences or thoughts welcomed.