I was the same (felt great for a while then a fog came back). I had to get my presuure adjusted (raised but not much) and the fog went away.

It triggered anxiety attacks in me.

I don"t know if pressurized air lessens the effect on hangovers, however I would be a willing test subject. (if it involves free alcohol)

I know the feeling. After I was diagnosed with severe apnea I would wake in the middle of the night and wonder "did I just stop breathing?" Hang in there, help will be on the way.