Male friends

I have known this guy for over 5 years.i really thought thAt we were good friends the fact that he was always someone i could depend on when i needed to talk. We spoke mostly over net. In person we would share a long warm hug a few word and depart and it was all good. We still engage in such behaviour however we live miles apart and hardly do see. Recently we stopped speaking for over 6 months. When i got sick being diagonsed to be bipolar he was not there to speak to. Now when i text him inspite of our long history he wouldnt reply. I am 19 and he is 24 with a lot more responsibilities. Have our relationship taken a turn for the worse? I miss talking to him but i do not want to annoy him. How can i rebuild our relationship?

I know that it is possible that he simply could be be busy however i have the fear that i may be loosing a good friend and i wouldnt want that. As far as how i feel about him i never thought of him more than a friend