Can’t change my country region

See this article:

Change your Apple ID country or region - Apple Support

Contact Apple Support

If you can't complete any of the steps, can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support.

Good luck!

I believe you will have to wait 90 days before you can change it again.

No. It's intended to keep people from illegally downloading content from stores serving countries other than their own.

Why are you changing countries so frequently?

If you're doing so to download apps or music that are not available in your country, that is a violation of the Terms of Service for the store and a violation of international copyright law.