Did I Seriously Just Lose All My Project Files???

VERY VERY distressed at the moment. There was NO WARNING about this and yeah, I'm freaking out. The amount of time and effort to recreate EVERYTHING is enough to drive me to tears. I didn't know I'd have to make a backup.
Basically what happened was I had Resolve 16 still. It had been running really slowly for the past couple of weeks so I figured it needed to be upgraded. NOWHERE did I see a warning of "oh hey, backup your project files, we're gonna delete all of them if you do this". I don't have a PC backup to go back to. Am I totally screwed over? Is there ANY way to recover my project files from 16 and put them in 18? If not I'm going to explode. Please, I am begging for help. I'm just a hobbyist, this feels so unfair. I have enough going on in my life right now, I didn't need this to happen to me right now.

It's seems unlikely that upgrading resolve would delete all of your projects. The database containing them should have been updated when you opened resolve 18. Do you know where your Resolve database was stored? If so you should be able to import it.

Upgrades and uninstalls (through Windows) don't on their own delete or alter databases. In the case of version upgrades, you should be prompted in the database manager to update the database. Until then you will not see your projects in the Project Manager. But you should not update until you've backed up the database or at least the projects created with the earlier version. Once the database is updated, the project files won't be readable in the earlier version, in event you want to revert to it.

And of course regularly backing up projects and databases is a given, as you would backup crucial data in any program. The Resolve manual details numerous ways to do it.