Oscar went through a phase when he was chewing on me like there was no tomorrow.
A trainer suggested that each time he nibbled, to yelp loudly (like his litter mates would have done), then put him on the floor and ignore him for at least 30 seconds.
The yelping startled him and definitely got his attention - the word "no" was old news by that point - in fact, Oscar reacted to "no" like it was a game - he'd double his naughty efforts every time he heard it. He craves attention so much that it was a really effective way to get him to stop. Now I save "no" (combined with a loud hand clap) for really serious situations. (Pooping/peeing on the floor, shredding a good pair of shoes, etc).
I hear your frustration! I also feel like I have an out-of-control dog sometimes and that I'm the worst "mom." For me it's been one more confirmation that human kids would be a very, very bad idea.
