Advice please :)

[WeezyF]

Hi all :)
I'm wondering if anyone can give me some advice on potty training..
I have a 3 year old almost 4!!
We've been on and off trying since he was 2, it's been a great struggle as he has freak outs and screaming fits over it, he'd rather pee his pants than go to the potty or toilet 🙈 I've tried almost everything I can think of but he still won't go, I'm getting worried as he's one of the only children in his preschool that isn't using a toilet! He will be going to school next year so I desperately need to get on with it x