As your devices are sharing a common AppleID for iCloud, you’ll encounter all kinds of issues and unpredictable behaviour - including unintentional and/or unwanted sharing of sensitive/private information (including Messages). You’ll not be able to reliably maintain any kind of data separation.
The Golden Rule: Don’t share an AppleID between users. Each user should have their own AppleID for their own exclusive use - linked to their own primary email (and secondary/recovery email addresses and trusted telephone numbers).
You would be best advised to separate your digital identities and configure and use a new AppleID for your yourself or spouse.
After separating your identities, you can continue to selectively share purchased Apple Services, Subscriptions, Apps and Media using Apple’s Family Sharing features - should you choose to do so:
Family Sharing - Apple
Set up Family Sharing – Apple Support
Share App Store, iTunes Store and Apple Books purchases with Family Sharing – Apple Support
How to create a new Apple ID – Apple Support
https://www.imore.com/how-set-up-family-sharing-iphone-ipad