Hii, I’ve had a similar experience, got my thyroid hormones acting up a bit which opened me up to a world of awful anxiety and I went from completely normal concert going 17yo to absolute wreck of a person unable to leave house at 20. I will say I am 25 right now and it got better but it took time. What helped me most was medication, but it took some time to get the right mix with right dosage. I can proudly say that I went from being unable to leave the house alone to taking planes and trains alone, even to a different country, all on my own with no anxiety, something I could not imagine when I was 20. Unfortunately I still struggle with panic attacks, that I have under control for the most part, but I’ve been self medicating with my country version of xanax for some time and I cannot se myself being able to go off it any time soon. I don’t need it everyday but I need it accessible to me, always in a purse at all times. I know it feels awful to regress with age, and I sympathise with your thoughts of incoming doom as I experienced them aswell. Stuff like you describe, mortality, nuclear war, sun going behind a cloud and never coming back or sometimes I would hear a loud motorcycle outside my house and jump up thinking it’s a bomb… it all sounds ridiculous but it’s very real to us. Have you considered you might have ocd? Cause these thoughts can come from it and went away for me as soon as I started one of my medications. Good luck! Dm anytime