B.M.
Get rid of all pull ups. Forever. No more. Pull-ups are the most detrimental thing for potty training EVER INVENTED. Bye-Bye pull-ups. I would probably have HIM throw them away since he is a "big boy and doesn't need them anymore".
When he pees on himself, HE must clean himself and any mess he made on the floor or change sheets, clean toys etc (not at night, night is different). No emotion from you - just "oops, please clean up your mess. next time go in the potty". You can help him so things actually get cleaned up, but he needs to do it first.
At 4 he may be old enough to be able to put the clothes in the 'washer' so he understands he is totally responsible for himself.
You can also have him naked on the bottom on the weekends so he gets the feel of it. Again - HE has to clean up his own mess. You are done cleaning up the mess.
Some parents have their son drink LOTS of liquid and then take him to the potty every 30 min or whatever for an entire weekend so they get the "feel" of what it feels like. I didn't have to do that, but they say it works, so you might try that.
GOOD LUCK.