Hi! It is difficult when someone we love doesn't respond to us properly. There could be so many reasons your friend isn't talking to you. Speculating about these reasons will only make things more stressful for you. Please talk to him directly and ask him what the concern is. If it is something you did that he is upset about then apologise and do what you can to make up for it. However if he is not telling you clearly despite your efforts and you are also sure you haven't done anything to upset him there is no point stressing about this relationship. Take this as a learning experience and move on to make new friends. Teenage is a time when there are lot of changes that place in our social life. You will have to accept move on.