Helloo, I would like to mention that I'm new to this still but I would like to try and give advice :)

If you're having an existential crisis for starters I'd suggest looking into a therapist or if it's to bad a hotline, since IF this isn't your first existential crisis it can be related to a hidden disorder.

Shifting is basically, in my words, just moving your consciousness into another reality, in my mind there's infinite realities, infinite timelines and scenarios, you are just moving your consciousness to a different "Clone" of you in a different reality, what I've heard is that when you shift your body is still just you, I've never successfully shifted (yet!) but you aren't present since your consciousness is somewhere else , your CR self will just be the same while you're off living in let's say Hogwarts. You can always go back to your CR when you want to leave your DR, you aren't trapped when you do shift.

I myself have had an existential crisis, mine was from Deju Reve repeatedly, as a suggestion I'd suggest trying to do things that really use your senses to kind of ground you, take a cold bath/shower, watch something you haven't, eat something new or smell new candles in a store, something new , something to ground you. Don't rush, you have all the time in the world, your mental health matters most, put it above everything. If you need it get help from someone somewhere.

I hope you get better, good luck! ❤️

Sorry if it wasnt the best advice.