The Source Of Jealousy
You may have acquired this behavior through past experiences with girlfriends. If you have already been cheated on, this may cause you to be more possessive and controlling of her for fear of repetition. Even if she’s never given you any reason to doubt her, you become increasingly desperate to hold on to the relationship and want to avoid potentially hazardous situations at all costs.

Similarly, you may be the one who’s been unfaithful in the past, and, in a shameful attempt to not have the tables turn on you, you want to ensure that you are the sole object of her desire.

But, for the most part, jealousy is a byproduct of one’s own issues with self-confidence and self-esteem. You may feel that you’re not good enough for her and that you’re together by fluke. Most other guys seem better looking to you and you feel threatened by that.

Watching her interact with other men leaves you feeling worried that she may be “stolen” from you. If you’ve only been with her a short time, you may even be bothered by the close bond she has with her male friends, whom she’s known all of her life.