How to potty train boys?

I’m so tired of potty training my strong willed nearly 4 yo boy. We have tried rewards with candy and stickers and toys. We have tried commando and pull ups and picking his own undies. We tried the potty watch and timers. He just wants to keep playing and refuses to go the bathroom otherwise it’s a giant emotional meltdown with him. He was doing so well there for a minute only having like 2 accidents a day ish and then he regressed so badly and I can’t pinpoint why.