Constant bad thoughts

Recently I keep getting a whole lot of random thoughts that won't go away, thoughts about death, about how little time we have, thoughts about the sense of all this, there being nothing to do, and they won't go away, and when it's dark in the evening, the thoughts pile up, having me almost panic, and it doesn't help that I have ADHD, making it that it takes me way too long to fall asleep, and pretty much anything I do triggers them, being alone, being with my family, being on social media, playing games, and doing things like taking walks around my area or being outside doesn't help, and I'm also in a a pretty small village, meaning that I can't get out or to any of my friends. I'm just looking for a way to stop the thoughts.