I feel you so much. I used to have extreme existential anxiety so much so that sometimes I couldn‘t sleep. Lately this has changed I can’t exactly pin point why but there’s a couple of thoughts that calm me down. Firstly we as humans always think we have it all figured out and we know what happens after but even if you are atheist you don’t know what’s going to happen and probably never will. For me the fear that there’s just nothing after death just lights out was scary but how would we actually know this is going to happen, we see ourselves as omniscient although there are so many things that we will probably never discover or understand.
You have to learn how to live with the uncontrollability and uncertainty of it. Secondly time passes anyways and death is inevitable no matter what you do. If I worry or if I don’t worry I’m going to die, might as well enjoy my time. Life is absurd. I think my existential dread calmed down a bit when I started reading Camus. Maybe life doesn’t have to have a meaning. If you’re interested in philosophy i definitely recommend reading Camus or there’s also youtube videos that summarise his Philosophy. I really liked „the fall“ and „the stranger“ and am currently reading „the myth of Sisyphus„. Maybe some of these things resonate with you :))