It's possibly just anxiety from your overthinking you can try inhaling for 4 seconds, slowly releasing it for 6 seconds, do this for a few minutes before sleeping, i had the same problem it helped me a alot, lemme know if it works for you!

Going to bed at the same time every night has helped my body sync into a routine and now I wake up naturally at the same time but it took me a while to figure out what the best time was for me.

I struggle with overthinking too, I’ve found somatic exercises really helpful. Have you tried the breathing and meditation practices here? They’ve helped me a lot.