He's jumping - go for Off and Sit - good puppy!
He's asking for attention when you're doing something else - down - good puppy!
Often with "NO" people make direct eye contact and stay focused and intense. The pup, not knowing what the heck is going on, either folds their tent (which people generally interpret as they "learned") or they mirror you back to you (they get focused, intense and assertive).
It is much more about confusion than anything else, generally.
So what are you "NO"ing him about - maybe we can help with that?
He's mid teething so probably pretty cranky and sore himself.
How much rest is he getting?
Does he get to play with other dogs at all?
What games/exercise are you using?
