Re: Are my teeth ruined forever?
Yes, if your teeth are angled the wrong way, braces can fix it. Even if you start later, like in your 20s.
But first you'd need to find out if it's actually your teeth that are the problem. Have you mentioned the pain to your dentist? Or your parents?
You mention clenching your teeth a lot. This can cause pain in the muscles around your jawbone. Opening your mouth wide and moving your jaw from side to side a bit can help relax it, so can gently stretching your neck.
Also, ask your violin teacher or another student who plays the instrument to help you figure out how not to clench so much. If it's too painful, taking a break from practice might help.