You need to think carefully about what you really want. If you decide you want to leave this relationship, you then need to tell her as soon as you can and you need to tell her the truth about why you want to end this. You need to allow her time to cry, get mad, and go through all kinds of emotions that may come up. If you feel you were too young, tell her. If you think you just feel like you are not right for her, tell her. Either and any way- talk. But be prepared for the worse. You are breaking someones heart. Be gentle.

Dating for four years. Have you enjoyed all the benefits of being a couple for this time period? What is the matter sweetie, has the sex slowed down? Think long and hard before putting an end to this relationship, most people don't stay married for four years anymore. You may not find any better than what you have right now.

I think the best thing to do is launch a serious attack on the "becoming bored". We tend to think of the deep, slightly disturbed girls with hidden secrets and hidden fire as more desirable than our ordinary steady loves, but believe me, its a horrible mistake. You end up facing the same "boredom " problem three years later, but with a crazy self-obsessed loony on your hands, who loves no-one but herself. Confess the problem to your girl, and set out to solve it together. Maybe she is even feeling a bit the same. But don't think of involving other people sexually, its not necessary, and for almost everyone it is destructive and kills the relationship. The best bond is to find something to try to achieve, which needs and absorbs both your efforts. Two people working together for a single goal. From what you say, I'd be surprised if you have even scratched the surface of what sexual love can give you in the "avoiding boredom" department. Set out on a journey together, discussing strategy, reading books, watching porn perhaps, and experimenting how to drive each other completely insane. If none of this appeals in the least, but you just have to explore other girls, then so be it. You have to do what you have to do. They are all amazingly different, and yet also amazingly the same. In the beginning you see only the first. Later you begin to see more of the second. Ultimately, according to some religions, you see, their is only one woman and one man. Her and you. You are locked in a cosmic dance, using body after body, endlessly trying to reshape the encounter into into a more acceptable form. But its all unnecessary, always in your arms it is the same one girl. When you finally just truly accept each other, it is done. Sh*t, where did that cosmic tear come from ? - its just a stupid answer posting game.