Dry mouth and locked jaw

I have a strange problem. for the past year my tongue seems to stick to the roof of my mouth and my jaw feels extremely tense and uncomfortable. it's hard to explain but it's as if I cannot get the lower mouth/jaw to relax and my throat feels like its closed all the time. So, if I want to sleep with my mouth open as my jaw can then relax (in theory!) I actually have to suck my thumb but then I end up biting really hard on it which hurts! I have been given a bite raiser by the dentist which sometimes helps but I notice that I often take this out during my sleep!!! this condition also causes me to have slight panic attacks as just as I am drifting off to sleep, my throat closes up and I can't breathe properly, my heart then skips a beat and I startle awake!!!! My mouth is constantly dry and my tongue is starting to feel like it's too big for my mouth! Any ideas?????