How do I tell a guy I dont want to continue being with him when he goes back to college?

He and I started talking about a month ago, and we talk every day pretty much. We have hung out and cuddled and kissed but we aren't anything official, and I want it to stay that way. He is three years older than me and when I go back to high school in the fall he'll be going back to college. I really don't think its a good idea for us to get serious, and I don't want it to continue when he goes back to college because I want him to enjoy the whole college experience without all the added drama (he had a terrible first year), and I want to enjoy my junior year without having to worry about a boyfriend. I have told him this already (before we ever hung out) but he just keeps saying "well what if I don't want to talk to any other girls in college?" and "Lets wait until the end of the summer and see if you feel the same way"...I know I will and I don't want him to get the wrong idea. How should I address this with him again without making him feel bad or making him feel insulted? because I really do like him I just want to be free throughout high school...working hard in school is stressful enough without the added drama of a long distance relationship