I agree with you that a 9 month relationship is perfectly fine (and can be a sexual one). The vast, vast majority of relationships don't last forever. It need not binary, where you date to be together forever or you don't see each other at all.
However, I have noticed that that very sort of binary thinking is big with people who come on here for advice (which is the chicken and which is the egg is a discussion for another day). I chalk it up to that.
PS If he's a junior in High School, and you're a senior, then you were both drinking underage, if you live in the United States. You need to cut that out; you can get your parents into some massive legal trouble. And speaking of them, where the hell were they in all of this? Do they know you're gay? If they don't, then you should seriously consider coming out to them. If you have condoms in your bedroom and guys coming over who you are introducing them to, then it's only a matter of time before they figure it out. Better for them to know because you told them, than that they had to conjecture.
Because your lover was under 18, this can make for some major problems for you, and for your folks, too.
Sorry to be the bearer of the end of fun, but there are some nasty consequences if they are arrested for providing liquor to a minor, or you end up on the sex offender registry. This is regardless of sexuality, I might add. I would be raising these concerns if your lover were female, or you were, etc.