Are you sure that he is senses your nurves and doesn't do well or he is not ready to work without food yet?
We do a lots of training. We didn't qualify a couple of times. I am pretty much at the nervous break down every time I go in the ring and my dog DOES sense it and doesn't want a treat at all! If your dog takes treats from you before going in the ring then he is fine and he just needs to work away from treats. Sorry, I can't give you any advice about the nerves situation...my palms swetting 2-3 months before every trial and when I am there I am loosing my mind....but it is fun after all!
I would recommend to go to the trials and see other handlers and their dogs, especially novice ones. It will make you laugh...dogs take off to hump judges, poop in the ring, refuse to move, trying to destroy fencing, LOL!