Hey there!It sounds like you may need to try the "Sign Out Everywhere" function. This should help to solve some of your problems. Click this link to go to your account page.
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Hmm...that's definitely odd. It sounds like they might have access to your other accounts if they can keep getting in. Not trying to scare you, just giving you a heads up.
The case is with the right team. They should have a solution for you shortly.