At your age, two years is a really long time. It sounds to me like your boyfriend started thinking about where your relationship is going, and what he saw might have been marriage (eventually) and for a young guy, that can be scary. He is probably thinking to himself "Am I really ready to be in this serious relationship for the rest of my life?" He may think he hasn't experienced enough things in life, or enough girls. You didn't say whether or not you have been having problems before this break. If you have not had any problems, I really feel that what I already said is what is going on. And in that case, I think you should sit down with him and have a serious talk. Tell him you know about him and "Sarah" and that you are very confused. Tell him that your definition of a break is to separate for a little while to clear your head, not to start dating another girl! That makes it not a break, but a break up. Then it is up to him to explain himself to you about what's going on with this other girl. If he gets mad about it, and doesn't want to talk, then I am afraid it is really over. He may have taken the break to try it out with this other girl. Either way it goes, you will find out for sure whats going on. And if he did start to date this other girl and just throw away two years, then good riddance, you can find a more mature and more respectful guy anyways. Good luck.
My Boyfriend Broke Up With Me Right Before Valentine's Day Telling Me We Need A Break. And Now He Is With My Friend?!
Most often boys do not form strong interpersonal bonds. There are lots of reasons, partly due to the inexperiences of youth, partly due to greed, partly due to the desire to sample the playing grounds. If your relationship did not have strong bonds, then don't place so much of yourself in it. Forgive your old boyfriend, yourself and move on to other boys. Eventually you will find one that is a better fit for you and the bonds you form will easily survive eye candy.
Why don't you get it...he basically dumped you for your friend....cut the loser free and move on
You're right what goes around comes around. He's the one thats wrong and when he realize it and try to come running back , there's your opportunity to show him whats up.