Your boyfriend has approached you saying he thinks he needs to take a break from this relationship. This has caught you off guard for you did not see it coming. What do you do when your boyfriend says he wants to take a break? It's possible he just wants some time to himself and it has nothing to do with you or he may be having second thoughts about the two of you as a couple.
You have some choices of things you can do if this happens. You will have to do some investigating to find the real reason he wants to leave. If you find that he truly needs some time to him self just let him go, he will be back.
Look at yourself, how have you been treating him? Are you pushy or clingy. Do you always have something negative to say about him? If you are any of these things or more you need to try to fix it or he may never come back. He may of gotten tired of it and wants to move on.
Another approach you can take is just agree with him that some time off would be good. You may not really feel this way but say it anyway. This approach will put you in charge and throw him off. Be friendly about it like you really think its good, although you may be angry and hurt.
After he is gone do not contact him for a few weeks. He may be thinking that you were planning to leave him and will be wondering what you are up to. He will have to contact you because it may be driving him crazy after a while.