3yo will hold it all day rather than tinkle on the potty! Help me!!

My oldest kid (boy) turned 3 last month. For the last year, we have been letting him sit on the potty (first we just wanted him to get used to it, then to start using it). He loves to sit on the potty, probably because that's the only place he gets to use his tablet, and would stay there all day if we let him. But he absolutely refuses to tinkle or poop on it! We have let him try potty seats in every room of the house, but he generally prefers the real toilet. So I've been giving him watered down juice (a treat he usually doesn't get, so he drinks it in a hurry), and keeping him diaper free and letting him stay on the potty as long as he wants. We've done this for several days. He will clearly need to tinkle (holding himself, dancing, etc) and will beg to have us put him in a diaper. If we do it, he immediately empties his bladder into the diaper. If we hold out and don't give him a diaper he keeps holding it. Eventually he HAS to go an will let a little out, then starts crying and freaking out. At that point, I've always given in and put him in a diaper (though I'm determined not to do it today).The good news is that he has phenomenal bladder control and will be a rock star once he actually gets around to using the potty.We've been talking to him for months about ALL the advantages of using the potty, have offered him special treats and toys if he actually goes. We have read lots of books about using the potty. Watched videos about using the potty. He's seen me and my husband use the potty many times. Still, no luck. We have special underwear with his favorite characters, but he refuses to wear them.I'm torn between letting him just figure it out in his own time, and getting this show in the road so he can go to preschool. I've read a bunch of potty training blogs, but haven't found anyone in this situation. I dot know what else to try.Any suggestions????Oh, and, in case this maters or comes up, he ONLY poops when he's in bed. So I'm only working on tinkling right now. via /r/Parenting http://ift.tt/2ePg2ej