2. He became interested in someone who’s totally different from his girlfriend.
Sometimes, guys become interested in a woman who is different from what they already know. “My girlfriend is an extrovert and has many friends. This girl, on the other hand, is quiet and mysterious, and I was fascinated by her,” explained a teen. Unfortunately, there isn’t much you can do to prevent your boyfriend’s change of heart in such cases. If you notice that your boyfriend is acting weird, watch him carefully and let him know that you won’t tolerate him cheating on you.