With Facebook you can check and manage the devices that are linked to your account. Follow this thread in the Help Center: https://www.facebook.com/help/174571515935086/?ref=u2u In general you could potentially have a tracking app installed on your device. You could looks through the list of apps and there permissions to see if anything looks suspicious. You should reset your passwords for any account that might be compromised. Lastly you can backup your data, and do a factory reset.