Mobile subdomains

I add in wp-config

define(‘WP_SITEURL’, ‘https://’ . $_SERVER[‘HTTP_HOST’] );
define(‘WP_HOME’, ‘https://’ . $_SERVER[‘HTTP_HOST’] );

Now I can use subdomains – but now sites have one database.
when i save settings (share-logins) in my site
https://paxtoy.con for https://m.paxtoy.com settings are saved

Now save settings for subdomains (share-logins)
https://m.paxtoy.com for https://paxtoy.con – but settings from the main domain disappear (as the domain cannot save itself)

how to solve the problem?