Potty Training Woes

Cruz is three years old now and we have been in the early stages of potty training for quite some time now. Honestly, I'm getting a little concerned he has not taken to it already. Cruz is so smart and learns things quickly, but potty training has been down right difficult. He'll really be into it and will sit on the potty for a couple of days, then he looses interest and cries when you ask him to sit on the potty. Even his daycare teacher is getting frustrated.

We have potty training story books and DVDs. We tried singing cute little songs and rewards with stickers. We give him lots of praise and we have never forced him to use the potty. I can't think of what else to do. I really hope we have a breakthrough soon!