Some advice on how to deal with my 4YO behaviour

I'm awfully ashamed that he has turned out the way he is. I tried my best to give him the best upbringing, I've taught him manners, how to be kind to people, showed him the right and wrong ways but clearly nothing has worked and my parenting is all gone completely wrong.

The biggest change we had was that we moved and he has since gone to a new school but be loves school and doesn't seem to have an issue but he is getting really naughty and stubborn. He has been like this since he was 3 years old and now getting worse. He keeps on hitting and pushing other children as well as myself if I tell him off for doing something he shouldn't, he spits as well and blows raspberries. Every day he is following me around, rather than entertaining himself. I can't let him in the garden because when other children play over the fence he starts being rude, trying to hit them and throw stuff at them. He doesn't go on a smartphone or play any game consoles as I prefer one on one interaction as he does, he watches TV on and off during the day.

I cannot stand his behaviour anymore I am getting more and more depressed and down about it. I've tried reward charts, having a deep chat with him, I've given him treats for being good, I've let him become independent ie pour himself cereal, butter his toast, get his own juice, but absolutely nothing at all is working.

Going out shopping with him is a goddamn nightmare and ruins the entire bloody day, even going to feed the ducks I'm constantly telling him not to go near the water because he can fall in or the ducks can bite but again he doesn't listen at all. He runs around like a maniac, he pulls and touches everything, he doesn't hold my hand when I ask him to, he throws a tantrum when I tell him he cannot have x or y and it is getting embarrassing trying to keep my cool and then I lose my temper when we get in the car which I'm ashamed of.

I am so worried that either he has a behaviour problem or autistic. I will probably have to mention this to my health visitor even though she visited and said he was very well behaved (ha!) and a sweet boy.

Deep down he is loving and a sweet boy but his outbursts, tantrums, hitting children and his parents, not listening and running off is literally getting to me. He pulled down my curtains this morning, he put the bathroom tap on full and flooded the floor, threw sand at the children. I am so tired of dealing with him and night time is awful he is always getting out of bed and doesn't go to sleep at all til at least midnight.

I think the fact I am also an introvert means I am probably losing it more because evening times is when I just want to wind down and relax by myself after a long day at work or with him, so I'm just drained.