If you obsessively think about someone all the time are you likely to have this disorder? You don't act upon it, so the person doesn't have any idea that they're even on your mind, but no matter what you do you just can't get them out of your head. It's like the from the moment you wake up in the morning to the moment you fall asleep at night they are there, invading your thoughts, and you can hardly concentrate on anything else.