I grind my teeth

I grind my teeth at night. This is a new habit I’ve picked up in the past half year.
The dentist took a mould of my teeth using some weird green stuff. I felt like I had it stuck in my teeth for at least half an hour afterwards, despite rinsing, fishing it out with my fingers, chewing gum, and brushing my teeth. It probably didn’t help that it was the same colour as my gum either.
I received my lower jaw in plaster form a week later, and along with them came a little rubbery cap to put on my teeth. (It’s on the left side in the picture).
It’s difficult to sleep with, but not impossible. In the morning, I find myself chewing on it as if it were gum. I’m not sure if I’m chewing because it’s there between my teeth and annoying, or if this is just how much I actually chew at night even without it.