First of all, this is a tad egocentrical. You're telling the internet that it might be your fault, or that if you would have been in touch with him prior to his suicide, he might not be dead now. If you feel guilty then own up to it. Write about it. Pray, if you feel so inclined, about it. Anything but this. What are you wanting from people? For them to feel bad for him, or you? Have you gotten in touch with his family? Have you asked them if they knew what was going on? No? Maybe that's a start.

I realize I'm coming off as being harsh, but I'm not intending for it, and it's probably coming out since you're striking a chord from within me. Allow me to explain. He was your best friend, but was no longer when you stopped talking. You mention that "he'd follow [you] around every chance he got like a lost puppy," if this is true (I'm not saying it isn't, but maybe you should take another look on what and how friendships work), then that would suggest he looked up to you. When a person looks up to another, especially of the same age, there's probably a bigger reason afoot. Exploring that back then, through deduction by social dynamics, etc. could have been vital for you, and more importantly, him.

I also graduated from HS a decade ago. I have a best friend (we consider each other brothers now) and we continued that friendship after high school. We joined the military together, (we did not want to do this but due to shitty circumstances it seemed like the best option at the time), and were nearly inseparable then, not just because we were friends but as a support system. We both hit critical lows at different moments throughout our time served and after the fact. We were always there for each other, and a lot of that had to be over the phone, unfortunately. He kept me from killing myself, I can tell you that much. Again, please don't take this as me trying to make you feel guilty, or attacking you, but simply as a reevaluation on the entire predicament.

I would, if I were you, value certain friendships. Most especially after this, use it as reflection. I don't mean to say abuse the loss of his life, go ahead and mourn, but also learn from it. (I think that you most likely already have a firm grip on doing such (valuing friendships), considering our age, but if not, then I can assure you it is imperative to do so now... have you had an existential crisis yet?)