Potty Training Woes

O.k so I get that potty training isn't easy. I get it's differen't for everyone, but really,Really!!! SO here's what I've tried....potty training in one day....skittles/mnm's rewards.....Punishment.......talking.....potty watch ....and prob a few other things I just can't thinl of right now... It's been two years and while the potty watch has been the biggest sucess when shes not wearing it its awful so today ( she'll be 4 the 30th) We we're leaving preschool and I begged her to go she said no I don't need to waited till I put her in her carseat and then came the floods...then We go to ballett and I get home ask her to go potty she says no and the floods come again......then she ask me to play her vtech with her and i do and we're playing and i notice the carpet is a darker shade of blue you guessed it ...... I know she knows when to go because while not wearing her panties we never ever have an accindent ,but as soon as she puts anything over that tutu of hers its time to let the dam loose and the floods come.............. I mean I knew this was hard but really.....I'm litereally loosing hair from the stress. If shes not potty trained by september no preschool and she needs preschool. I have gave it over to the Lord and asked for his help, but help or not this is one stressed upset momma. I mean my child is perfect, polite,honest,doesn't have a mean bone in her body this is her only gliche and whhew what a gliche... She'd rather play pee and know she gets in trouble than take 2 minutes out to go potty and come back ......I know to someone who's never potty trained, or had a super quick potty training experience this may seem crazy, but I have cried form stress and feeling like im a failure as a mom so many nights. Is there anyone else out there like me , or am I just one crazy mom!!!!!