Feeling sad

So about 3 months ago I became friends with a guy from highschool. We never talked then but now we do. We graduated 2 years ago and we talk everyday now. I have feelings for him and he recently admitted he has feelings for me. I thought that the only thing stopping us is the fact that we are bestfriends and he said that if we break up he doesn't want to ruin what we have. At first I thought this was a bullshit excuse. He just told me he was thinking about joining the marines at first it didn't hit me and I told him I'll miss him and I think it's great and I support him. But he told me today it's official he's going to boot camp in May. He said that it's the only reason why he doesn't want to make it official because he'll be away for a long time. It just hit me today that's he's serious and he's going to do this. Am I selfish for being heartbroken now?