My first thought when you say that your horse isn't responding to your bit, and that you're riding western, is that this horse isn't trained to respond to leg and seat aids, and that you're relying on the bit a lot. When you upgrade to a curb bit, that is supposed to signify that your horse is so well trained that it can have this harsh bit in its mouth, but it rarely has to be touched; the signals come from the rider's seat and legs, and lastly, in the form of neck reining.
If your horse is heavy on the bit, and you're relying on the bit a lot, please switch back to a simple snaffle (no leverage; don't be fooled - any bit with leverage is no longer a snaffle, even if the manufacturers label it as such) and go back to the basics. Once your horse is responding to a snaffle, then pop the curb in for show; you shouldn't be using the bit much though. My recommendation is a western dee snaffle perhaps with copper inlay to encourage salivation.
That your self taught is wonderful, but EVERYONE reaches a point that they need outside help. Everone; no matter what level you're at.
