obsessive

/əbˈsɛsɪv/
adjective
  1. Thinking about something or someone too much, in a way that is not normal or healthy.
    • The fan's obsessive interest in the singer's personal life worried her friends.
    • His obsessive attention to detail made him a great editor but a difficult coworker.
    • She has an obsessive need to check her phone every few minutes.
Antonyms
noun
  1. A person who has very strong, often unhealthy, thoughts or habits about something.
    • He's a bit of an obsessive when it comes to keeping his desk perfectly organized.
    • The group was full of obsessives who could name every character in the series.
    • As a fitness obsessive, she goes to the gym twice a day without fail.