Potty Training, Day 1- A Nightmare Starts

I think im going to pull my hair out before this is done. I thought life was stressful before this! was i wrong. This morning at aproximately 9 i decided it was time to put zach in big boy underwear and start potty training. An hour and a half later, after sitting on potty four or five times, then giving him one cup of juice, he pees, not in his potty, but in his underwear right after getting up! ugh! well, went back to potty just to sit there fifteen minutes to not go. Well, changed undies and what happens, we eat lunch, one cup and i was gonna wait about ten minutes. Hadnt no more put him down and he pees, in his clean undies, all over the floor. I hurry him to bath room just to repeat the process!!! four underwears, three messes, and no pee in potty later, mom was ready to scream!!!! i know it cant happen over night but come on!! i then decided it was nap time, with diaper on!
Well, need less to say, im a little discouraged. I wish i could snap my fingers and make it happen! He is two and a half and i know its time to do this so i know i just gotta be patience. I have never had patience!! its the hardest thing i have come across yet being a mom, and im sure i can manage this hurdle. Once i figure out how. I tried the candy thing if he went in potty, and he never went in potty so that didnt work. he would wait till after he got off potty to go! so please, i would love some advice, encouragement and prayers that this is an easy transition.
I know it can be done, but its gonna take time. Zach is smart, but i dont know how he will learn to pee in potty before his new bid boy undies wind up soaked!! So i think ill put pull ups on, then try undies again in the morning. Lets cross our fingers and hope it comes along, before we go through more than a doaen pairs of undies a day!!!! lol thanks!!!