Please don't worry. It will click. Patience is the key with this....I know because my four year old (birthday may 1, 2005) just potty trained this last summer after his fourth birthday. I went through all your feelings...but am now receiving articles from newsletters that it is perfectly normal for some kids to train at four. Where were those articles when I was panicked I do not know.
I noticed a few things with my son. Ultimately it is his decision and he hated when I was always reminding him. This is what we did. Forget about nighttime for now...who cares. I put him in underwear when we were home and pull-ups when out. I did not remind him. Yes we had A WHOLE LOTE OF ACCIDENTS. Get a bissel! After a few days he started running to the bathroom after he went in his pants. I thought that was a good step. I stayed positive and cheerful and let him know he did good but needed to try to get to the potty a little sooner. During all of this we had a BIG prize up top the TV waiting. One for the first pee by himself, then one for the first poop, then one for staying dry and going out in public bathrooms.
It took us a month or more and I did think I was loosing my mind. Then one day I was upstairs and I heard the toliet flush. He said he went. I went back upstairs and a while later I hear him running...I ran to the landing and yep...he was doing it! Then came the poop later and public restrooms took a little longer. But we have been going strong since.
One thing my little man wanted I think was to stand an pee like his daddy and the other bigger kids he saw. He is small guy. It wasn't really until four that he could do that and was tall enough!
My best advice is RELAX, pick a "program" for lack of better terms and stick with it. My son accomplished everything "later" then the "book" said he should. But I saw intelligence there that I could not place on a milestone chart like logic and reasoning. I wish I did not worry so much over when things would happen......it only stressed me out and made my son and I unhappy at times.
I also may not try this over the holidays. Jan, Feb, March are boring months where you may stay home more. The holiday's are so exciting and schedules are often different that might make it harder.