What type of sleep disorder(s) could this be?

I’ve been a lucid dreamer for as long as I can remember, and my dreams have always been mostly pleasant (at least since my early childhood). Lately, however, I have been having the most terrifying nightmares everytime I sleep, as well as dreams-within-dreams and I often wake up with an unshakable feeling of an encroaching, suffocating darkness. I have to sleep for at least 12 hours to remotely feel satisfied, but I am unable to go to bed when I am merely tired. I have to exhaust myself in order to fall asleep without having racing, jumbled thoughts or the feeling I should be doing something else, like writing, building something, painting, reading, or drawing. What could be the cause of this? It’s beginning to interfere with my day to day life.