Is it normal to clench my jaw in my sleep?

sorry to hear. I sometimes contract certain facial muscles when sleeping. I can tell you it's most definitely related to stress though. Often you may think you're not stressed but the only difference is you've become emotionally desensitized to it. body language is the great tellsign

Have you tried sleeping with your mouth open? I mean it's not the best solution but is the lesser of two evils. And theoretically seems like the most anatomically relaxed position for a jaw. I've noticed some people sleep with their tongue out just a tad, if you can manage that, maybe it would be enough of a negative reinforcement to stop clenching your jaw? Just throwing theories at this point. Try to relax your jaw and face as much as you can before sleeping.

Similar, my jaw is weird, its not overshot or undershot whatever it is when the bottom is in front of the top, but they are at the same level yano?
Anyway I have had jaw ache in both sides for as long as I can remember around the bottom of the jaw, my teeth aren't great and the orthodontist told me I could have my jaw sorted out with surgery. I mentioned the pain to my normal dentist as he said the aching is coming from me grinding my teeth in the night.. my teeth aren't wearing out and it happens a few times a year, I wear a retainer anyway and hate it haha. But it is painful when my jaw starts playing up. I don't honestly know because mine doesn't happen that often and when it does im not stressed, maybe have a word with your girlfriend and your relationship.