Minecraft is struggling - will not load properly

So, My Minecraft won't open. It will load onto a black screen, but then I will just close - sometimes it will close after a few seconds, sometimes it takes longer than 5 minutes. I've tried shortcuts and opening from the search bar, but it didn't make a difference. I'm afraid to uninstall and then re-install because last time I did so, I lost all my worlds and builds. I just don't know what to do lol.