Sleeping with mouth open but not mouth breathing, tape not working

I think I am sleeping with my lips slightly open, but when I wake up, I am still nose-breathing, but my mouth is dry and my tongue is sore.

I tried taping my mouth shut with surgical tape, which worked great, but was really sore on my lips when I removed it, so I used a tiny bit of tissue to protect them. But the last two mornings, I have still had my lips slightly apart under the tissue when I woke up. It’s like the muscles have just got loose. A strap would definitely not help, as my jaw doesn’t need to move for my lips to part.

My gums have started to recede, so I am really worried about my teeth. Dental X-rays previously showed I have terrible bone structure (like a smoker’s - but I’ve never smoked), but then my gums were super healthy, so I was ok. But if I can’t fix this, I fear my teeth will start to fall out. I am 50 years premenopause with a slight overbite on thetop, maybe this has something to do with it.

I really hope someone here can help me as I am really worried about my teeth

Sorry, are you using the CAP machine? or why did you try the tape? if you are using the machine request the vendor to put the correct compress air level you need.