Tracking my current device location

it has become apparent to me that my Sister has been, and continues to be tracking my current location and history, as well may have access to other critical data, through our communication, iMessages, iPhone and/or email.

1. I have already executed the suggested Apple iPhone security measures.
2. Turned iPhone off and restarted using a different Apple ID, then switched back to my regular iCloud Apple ID because it is linked to my phone and number.
3. Read privacy and transparency report and there is nothing indicating anything about my contacts or any breach of privacy.

what can I do to check my phone to see if my Sister and possibly her husband are able to track my device?