Potty training Nightmare day 1

And it begins. I had to break down and just decide that we were going to do this and I am hating myself at this moment. This was the least crazy of weeks and weekends coming up so I just had to. well needless to say it isn't going to be easy. Braxton has always been good about going Pee on the potty if you ask him too, he has been going a few times a week for a few months so I didn't think that was going to be a big issue. Well then today happened he was doing great for about 4 hours and then he peed in his undies, OK no big deal lets go sit on the potty, well cue the meltdowns, he yelled and screamed and this ended up being an all day thing every time I asked him if he had to pee he would freak out. he has peed in 3 pair of shorts one in his room and twice on the carpet.. Bring on the fun.