How do I make my leaving easier?

"Right now I love him but when I leave it might change. " That to me sounds like the key phrase right there. Love is something that lasts forever (or a very long time. ) If you are already having doubts, then it probably won't last between you two. Plus, college will be so much more enjoyable/memorable/better if you can date other people freely without having to worry about a long distance boyfriend back home. You are still young; you NEED to date a lot of people so you know who you want to spend the REST OF YOUR LIFE with.
By the way, have you talked to him about this? What are his thoughts/feelings on this?

There's no way you can make him understand that, he has to do that on his own, all you can do is sit him down and talk to him, explain how you feel. If he really loves you, yes it'll be hard for him, but he'll also understand that you're going off to live your life and if it's meant to be it'll work out in the end.

Well. I feel that if both are you are truly in love - then it won't just disappear and you won't be able to just find someone else even though you're a flirt. So if you're really not in love with him in the first place then break it off.