I have developed a strong and scary dizziness

[Tampa Jim]

BPPV is most likely the culprit. I'm blessed with Ménière's disease and it's a PITA and beyond. Nothing like being inside the Whirly Go Round at 500rpm for 3-4 hours. Please visit an E.N.T. and have them be sure it's not something else. Once you've passed any testing, a good physical therapist can assist with BPPV.

[UnicornRider]

I agree with Tampa Jim, even though you may feel as if it is CPAP related, do get it checked out. There very well could be underlying causes that are only manifested while wearing the CPAP. Even though you feel fine without the CPAP, it can cause problems later on, like boiling a frog, you don't notice the onset of problems until they become noticeable to others.