If you want to do this just to let your feelings out to the world (because believe me, it does feel nice to let all of that out), then I say go for it! But just be careful that he may not feel the same way so you need to be ready for whatever answer he gives you. So if you think that you are ready for any kind of answer and you want to unburden yourself of those secret feelings (they do feel pretty "heavy" after a while), then I don't see the harm of telling him how you feel.
Also it does help if you think that may like you back. If you think he does, then telling him won't be such a bad idea. But if he's clearly showing signs that he isn't interested, then this isn't a good idea even if you do want to let all of your feelings out because you may be in for more than just a "no" for an answer and I wouldn't want you to get your feelings hurt.
So yeah, weigh out the options wisely and good luck!
