Is it okay that my veneers shift a little bit? I am positive that it happens when I play saxophone. (Photo)

I am a classical saxophonist going into my master's degree program. A few years ago I got porcelain veneers placed on my teeth. My teeth feel weak and hurt; sometimes sending pain through my head. The spot in the back when the veneer meets the tooth (near bottom), a night with my retainer it is flat. After playing, when i scrape my nail on the back of my tooth, I feel almost a half millimeter of the veneer away from the tooth. This is very important to me considering it will be my career.