Now I have space inside to assume a nomal position and I never miss the box. Another cause of missing the box is a dirty box. You should pick it out every day. This is especially important when more than one cat is using the box. Now, the nervous cat - well, I think you have a nervous, active cat.
Some cats are like that, expecially thouse that are part Siamese.
If this bothers you, try to avoid getting a cat with any Siamese blood the next time. Persian type cats tend to be more relaxed. With mixed breed cats from the animal shelter, or from a private home, you do take your chances with temperment. I camne from the animal shelter, and I personally am high strung. I used to be very active, but I am not noisy.