My boyfriend wants to leave me because he says it’ll hurt too much when I go off to college in a year and a half, I think that we should stay together until I leave. How do I get him to stay ?

I am sorry to hear that you have situation like this. First your boyfriend made a decision that he thinks is the best way to deal with the situation. You can do much to make him stay with you except talking with him honestly telling him how do you feel about him leaving you. Another thing is why would you two separated when it is your time to leave? Maybe the is a chance for you two to still be together. But that should be discussed between you two. What ever happens try to respect his decision in the end.