Mark made a bet with his friend, if he could make you his girlfriend his friend would give him money and a car. And he succeeded, he made you his girlfriend, but he has no feelings for you at all. He just waited for your relationship to run for 3 months after that he was free from the bet. And without realizing it, it turns out that he also has feelings for you, only he is in denial about his feelings. And you didn't know the bet until the moment you found out, you felt fooled by Mark