How do I train my brain to relax again?

I'm on day 25.

I am not sure I ever successfully relaxed before I first started smoking at 18. My brain goes a constant 100% pure chaos all the time. When I was younger, I suffered constant hypervigilance, depression, anxiety, and stress. Smoking was the first time I ever felt my brain truly relax.

Now, I'm trying to learn to function as a sober adult, and I'm having the same problem. I cannot relax. I work out. I do yoga. I watercolor. I use all my coping mechanisms from years of therapy. Nothing gets my brain to slow down and feel calm. I don't even relax while I'm sleeping. I have stressful dreams for what feels like the entire night. I will literally wake up gasping from the dreams.

I know I have some other issues... undiagnosed neurodivergence, PTSD, clinical depression, and generalized anxiety disorder. But I figured that quitting would help me with those things, instead I've taken away the only thing that gave me a minutes peace and quiet inside my brain.