Why is he doing this? I don’t understand...?

I have been dating this guy fro four weeks now. We live far apart so we talk on the phone and skype on days we can’t se each other...which is only once a week. We have talked about everything, have had some great heart-to-hearts, he told me I was beautiful and wonderful, and told me I was worth the drive. On days he knew we couldn’t talk in person he would leave me sweet voicemails or a simple text message saying hope you have a great day. Then last week a day went by that he didn’t call. I thought it was weird, but blew it off. The next day nothing so at the end of the day I texted him. He replied back, but only two times. I figured he was just busy so I blew it off again. Then two days went by before I finally texted him again. He replied only a couple of times then too. By this point I was getting a little worried. I knew he was the type of person to always want contact. The next day at about midnight he called me and told me why he hadn’t called the day before and so I stopped worrying about it. Then two days went by and nothing. I texted him finally on the third day and once again only two replies. I texted him the next day and asked him if we were going to hang this weekend and he said that he had to train for a thing he is in. This caught me totally off guard because when he left after the last time we hung out he was anxious to see me again.....so why is he doing this? What happened? I don’t understand?