As someone who was in a long distance relationship with my current boyfriend for nearly two years, I have to tell you that communication in these instances will make or break your relationship. This is what you rely on when you cannot physically see one another. That being said, if one person is unwilling to communicate with the other--how do you keep a long distance relationship alive? The sad fact is, that some people are just not cut out for long distance. The lack of physical proximity, jealousy issues, and temptation can prove to be too much. Since you're under 18, it may also be that he is simply not ready to be in a mature relationship like this. It's easy to tell someone "I love you" at that age, but I think a lot of people find themselves unprepared to be able to do the work to maintain a relationship, especially a long distance one, when they're so young.
If you find that things are deteriorating like this then you may want to consider to moving on. You can't have a long distance relationship with someone who isn't willing to communicate with you. He may just be avoiding you hoping that you get the idea because he's just to scared to tell you. He might be interested in someone else and again, may just be too scared to tell you. Or maybe he just feels like it's too hard and he's just content to let things die without wanting to explain himself.
So you do the mature thing: Call him up and ask him what the deal is. Say while you care for him, you're not willing to stay in a relationship where you have to do all the work. If he's not interested in being with you anymore, all he has to do is say so. Leaving you hanging on like this is unfair and is keeping you from finding someone else if he doesn't want to be with you. If he does still want to be with you, then it's time to lay some new ground rules about the way that you communicate in your relationship. If, after a while, you see things beginning to slide back to the way they were--then it's time to get out. If he's not willing to follow through and make the extra effort along with you, then don't waste any more time. There are plenty of other guys out there that will treat you like you deserve