It's very common for teenagers in particular to not reveal or act on feelings that they have for friends due to a fear of ruining the friendship, or as you say, ruining what you have. In reality, whilst there are circumstances where it's probably best not to confess feelings, I don't generally think that the broad fear of ruining the friendship is a good one. I say that for a few reasons. First, friendships come and go, and strengthen and weaken, throughout your life. It's very much a natural part of getting older. There is absolutely no way to guarantee that friendships that you have now will persist for even a few years more, let alone for the rest of even the majority of your life. That obviously doesn't mean you should be reckless with those friendships and not care about them; the point is that it doesn't make much sense, in my view, to not take something like this further for fear of ruining something that may naturally drift or come to an end anyway. I didn't pursue relationships with a couple of girls when I was your age for that reason, and both of them had the same feelings for me, but we both decided in both cases that we didn't want to ruin our friendships. As it happens, I'm not in contact with either of them anymore, and haven't been for a good 15 years. Does that mean we would have had long lasting and meaningful relationships if we'd pursued them? No, it doesn't. But life is about gathering experiences, and with hindsight, there really wasn't any good reason not to pursue those relationships.
Beyond that, on the issue of coming out to your friend and revealing your feelings, if it is a strong friendship you should be able to come as you are, that is to say that even if those feelings aren't reciprocated, your friend and the friendship as a whole should be able to acknowledge that and deal with it. Could it make things awkward? Sure. But it equally might not do. In any event, having a strong friendship with someone means being able to be vulnerable with them and trust them to make you feel secure in that. To my mind, this falls exactly into that category.
For completeness, it does sound to me like there are some signs here that your friendship is straying here and there into the more romantic side anyway. Not enough to be definitive, but there is some reason to think he may want to go further. Or it could mean that you are just very close friends. Either way, it's something that would cause me to encourage you to pursue this. Ultimately, you don't have nearly as much to lose as you think.