Login Location Error??? See if what I enter below is descriptive of what happened to you.
If you received a notification that someone else is logging in under your Apple ID about the time you were doing so, everything probably is OK. The location in the notification is where your ISP reported your login. If their servers are in a location different from yours (possibly quite different from yours), then the notification you saw is a login location error. For safety, change you Apple ID password https://support.apple.com/en-us/HT201355 Here is what to do after you change your password https://support.apple.com/en-us/HT204071 Also, remove any device shown in your device list you don’t recognize using Check your Apple ID device list to see where you're signed in https://support.apple.com/en-us/HT205064