Stress can do things to you--and you can be so completely unaware you are under stress--that it's shocking. For example, a couple weeks ago or so I was going to have a colonoscopy. Every time I was telling someone I was going to have it I would not be able to pronounce the word on the first few tries (colon-os-copy). Trust me, I'm pretty articulate, so I thought that was weird that I kept stumbling over such a simple word...but didn't dwell on it.
So, I have the colonoscopy, the Dr. said "looking good" to me afterward...and viola! I can say colonoscopy without stumbling immediately. Naturally, the light bulb went off as to why I kept stumbling over the word before, but, if you had asked me if I was nervous about going to have the colonoscopy I would have said "no."
Of course, I realize now it was unconscious stress on me cause my Grandma died of colon Cancer, and I lived with her for awhile during the end and have always been afraid of getting it.
Unconscious stress can really do you in without your even being aware of it. Hence, the tooth clenching. Just my theory, anyway.
Please consider adopting a rescue animal. So very many need a furr-ever home and someone to love them! And if we all spay/neuter our pets there won't be an overpopulation to put to death.