girlfriend i feel you pain....
we had the EXAT same problem for the EXACT same reasons and reacted the EXACT same way.....as dr. phil would say, hows that working for you? lol
it is his only way to be the star right now, even if its a bad way...as far as his little mind thinks...punishing, getting angry, belittling, wont do a thing.....we did all that and it grew to be more of a power struggle, and by belittling i dont mean on purpose, but anything negative about it at this point will just take him down.
so what did we do? we stopped making it an issue. every time we tried to get thim to go to the bathroom turned into a confrontation...so we stopped asking, we acted like we didnt care one way od the the other....we cleaned up the mess without a word, gave him kisses and hugs and cleaned him up....after 5 days, he started pooping in the yard(weird i know), after 10 days, when we'd giciven up and decided that hed figure it out by kindergarten, he casually came into our office where we were and announced he just pooped in the potty.we all rejoiced, and there was NEVER another poop accident sice.now naptime, if he didnt pee befor nap he would have na accident. he is 5 now and still wears a pullup at night, dr. said his body is just taking a little longer to develop the chemicals used to alert bladder during deep sleep and that it could take until 7 or 8 max but dont sweat it. but once we stopped getting angry, making the pooty issue a big deal, it no longer was one.and they hate being all yucky, whether they admit it or not.
we even had in preschool 2 days a week too. and it helped...its all about the power.and he loves his brother and there were no problems, there was much more jealousy 2 years later than at firsrt....give urslef 3 weeks....he will come around!if my son can, yours will. he was dubbed "most stubborn student ever" at his preschool.lol.
hang in there and try to get some sleep in the day!
ps-one more thing-----do NOT have him in pullups, of course hes gonna go in them because he can!!! goodnights for nap and sleep are fine but otherwise NO WAY! remeber, they hate the mess too and it will expedite things for you...sucks at 1st and ull have to commit to clean up for a bit, but when they realize its big boy underpants time, they will stop.
every kid is different.what works for some may not work for others. this is what worked for us. he absolutely refused t oclean up his mess and would end up smearing it everywhere in rebellion. when i would say its time to go potty he refused fighting all the way in kicking the potty over, i mean u cannot FORCE/hold them down to do their business u know? i knew this huge fight wasnt the answer and it just made him feel worse about himself. taking the toys awya and priviledges...it just made him go deeper into himself and more depressed and didnt solve the problem at all....and geez, they are only three! 3 years in this world...i have learned over the years that little ones really do just want to please us.....they light up inside from our approval....if they are fighting the potty thing its ot about the potty, its something else and u know your son more than anyone...i bet he is a wordeful good little boy....and he loves you to the moon! rememebr that and hang in there....i know you are tired and wishing for a long bubble bath and a chance to shave your legs,l ol its will get better!