Should I stop being friends with this person?

I have known this person since we were nine, we are both sixteen year old boys, and he used to live behind me. When I first went to school with him he was more popular than me, but our roles have slowly reversed. Without sounding like a schmuck, I have slowly grown into a more and more outgoing person and he has become very possessive/ clingy of his time with me. As I have tried new things, taken different cles, met new people, gone new places, etc, he has continued to act the same way he always has- and up to this point people have just accepted it. He only likes to talk about himself, and if he isn't talking about himself, its something that absolutely no one cares about, or just completely embarring for everyone in partaking in the conversation. I have talked to him on two separate occasions about this behavior he displays, and he always promises me that he will quickly change- which he doesn't. More recently, I have made some new friends at my church, (which he also attends) and a good majority of my time has gone to spending time with them. Trying to be a good friend at first, I tried to get my old pal involved with us, but after quickly seeing how awkward he makes it with his lack of social skills, I have decided to keep from inviting him on several different occasions. Now, with my new friends being rather attractive girls, this doesn't sit very well with him. I've was able to avoid the problem until last Sunday when we went out to eat for one of the girls birthdays. The problem is, he wasn't invited to this lunch, but to another get-together with a guy from our Youth Group. I was invited also, but opted to go to the birthday instead. Why this is a problem was, my friend had left his wallet at home, and asked me if I could spot him. Like an idiot, instead of saying "I'm not going," I said "If I go I will spot you, just let me see what I'm going to do." Now, I know that he is good for his money and would have payed me back, that's not the issue. After church, he asked me which lunch I was going to, and when I said the birthday, he got offended and pissed, running off before I could offer him money to eat with the others, which I was planning on doing. I felt awful at first, but not I feel as though I should just wash my hands of this entire thing. I haven't spoken to him since. Should I try to get back together with my friend, or just move on? As of this moment I'm leaning towards the latter.