Keep getting Pcs add to my Account and they are not mine i only have one is my account hacked?

Hi keep getting other Computers adding to my account and they are not mine! I only have one laptop on my account and for the life of me cannot see how they are getting onto my account without me knowing I have spoken to customer service who delete them but they keep coming back in a few days is my Computer Hacked or some kind of trogon that gets into my account and adds there computers any ideas and have anybody see this before

 

Thanks

 

Labradorman