How can I find out if someone is logged in to my Apple ID

Check your device list to see if there is a device signed in that you don't recognize. You can remove the device using the steps in the article below. As a precaution, change your password.

Apple ID device list -Check to see where you‘re signed in.   * 

See who has access to your device or accounts

 Apple ID Password Change.   -  

ASC YouTube for How to reset your Apple ID password

 What to do after you change your Apple ID or password - Apple Support  -   I suggest doing this before you change your Apple ID or password.

Hello ~ Any help here…

See information about devices signed in with your Apple ID on iCloud.com - Apple Support

~Katana-San~