Can Someone Read My Texts Without Me Knowing?

To clarify active sessions, it's basically every device that's currently logged into your account. If you’re unsure how to find that, just log into your account via a web browser—there should be a section where you can see and manage all the devices connected to your account.

It sounds like they might have access to your Google or iCloud account. I recommend checking for any active sessions on your accounts. You can usually do this by going to your account settings and signing out of devices that you don't recognize. After that, make sure to change your password to something strong and unique.