A relationship with an expiration date

I don't want to leave Adrian, I like being with him. But I don't want to leave my house or city either, and I'm still doing that in the name of starting adulthood. I know I need to call it quits, it would be terribly unfair to drag this on when it's not going to go anywhere.

He wants to meet a girl and get married and all... so it would be mighty selfish to hold him back from doing that. Which is basically what I'm doing.

I will admit I am scared to say it's over for fear that I will not meet anyone new to call on weekends and have sex with and all. What if I say goodbye, and ruin everything, just to be sitting alone horny with no one else? But he's not only the sex of course! He is the closest person in my life. I have no other friends or people who hold a candle to what Adrian and I have. What if we could be happy for longer? Adrian is the only person I've ever gotten so comfortable with so the idea of doing what we do together with someone else is, truthfully, terrifying. This relationship grew over 5 or 6 years, and now it's all over?

I have the option of continuing past the university start date because I will come home on holidays and some weekends. But it feels wrong to do so when I know I will want to have sex with other people. So, what I would essentially be doing is using Adrian until I find someone new - all on purpose. That's not right, is it? It's easy and comfortable, but not right.

I think this is a strange situation because of my lack of romantic feelings. Maybe if I felt romantic attraction I would be lovestruck and want to stay with Adrian even with the 3 hour distance (isn't that what teenagers in love do?). But since I don't feel romantic attraction everything is complicated and unconventional.

I have to bring this topic up in our conversation soon. Him and I have not talked about it. Even though we have talked about how crazy it is I am moving 3 hours away we deliberately and unanimously ignored that particular elephant in the room. I want to wait until we graduate high school, so we can be blissful for one last semester and have a magical prom night filled with lots of sex and alcohol. We can pretend that it will go on forever.
Then, after forever has ended, summer nights will be filled with speculation and deep conversations about our futures.

Sometimes I wish I could fast forward to lecture halls and medical school, and other times I wish time would stop in high school labs and Adrian's room.