Yeah that's definitely worth exploring with a therapist. I mean most ppl like turn 10 or smth and realise they'll die one day, get super bummed out for some time and then try their best to never think about it again lol. That was me at least haha. But if it's negatively affecting your mental health then it's a good idea to address that with someone who can help.
We come up with all these reasons for why death is good and necessary, like "life is only special because it will end one day", or we subscribe to a religion, which I assume would make death a lot less scary. I mean to me it's pretty scary to think that one day your consciousness will probably vanish and you just stop existing. But then again, the fact that that scares me is an indication that I have reasons to stay alive. The fact that I don't want my life to end tells me that I'm doing something right haha.
But then also, like the idea of immortality is scary as well. Watching everyone and everything around you die, knowing that any friend you make or person you meet will leave you eventually, sounds incredibly lonely. And if everyone was immortal I feel you would end up dissatisfied because eventually you'll run out of new experiences, and the old ones will get boring.
I feel the best case scenario after death in my mind would be reincarnation. Because that's like a video game with infinite replayability. Starting fresh every time as a different person every time sounds cool. You wouldn't know you'd been reincarnated, but it sounds better than poofing out of existence or growing old enough that nothing is exciting anymore. Idk death is weird lol.