Recessed chin/jaw causes difficulty closing mouth & a lot of pain. Recommendations for best course of action? (Photos)

I have had difficulty closing my mouth forever. I have to clench my muscles to keep it closed causing a lot of pain, headaches, & tension in the back of my neck. If I don't clench, my mouth will open on its own. I also have to push my jaw forward while I eat/drink/speak. It's better to have my mouth open but after a while this makes my jaw feel heavy and breathing more difficult. My dentist suggests a bruxism device but I don't grind my teeth. I have an appt with an orthodontist for a 2nd look.

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