When/how to talk about this

Some context: I've been in a relationship with my boyfriend for more than a year and everything has been amazing. The problem is that he is a year older (senior now) and will be going to college after this summer and I will be staying and entering my senior of high school. I know that whether or not we stay together it will be really difficult, because there will be times where I won't see him in person possibly for a few months. This thought is constantly on my mind and it makes me sad and worried a lot, especially because I don't know his feelings on it. I am willing to stay together because I don't want to lose what we have (he is also my best friend and support) but I'm not sure what he wants. Should I wait until it gets closer to him leaving to bring this up even though it's on my mind so much? Or should I bring it up now and risk him saying he doesn't want to stay together? I don't see myself being able to be happy in the relationship knowing that we will break up by the end of the summer, if that does end up being what he says. Any advice on this, on how to talk about it, or how to make it work long distance is very appreciated, thanks.