Relationship problems

My boyfriend is 18 and I am 16. We were together for four months before he broke up with me saying that he is just bad for me and I deserve someone so much better than him. We were apart for about two weeks and my heart was broken. We weren't together for very long but we spent multiple hours every day together, which looking at it now was a bit much. Anyways, after the two weeks, he came to me saying that he can't live without me and saying even if we had to be just friends, he would do it. After about a week of us talking again, things started to get back to normal and we were a couple again. That was about a month and a half ago. He left a week ago for AIT (military training) for two months. I am having a really hard time being away from him, he is really my only friend at the moment. He can call usually about once a day and always sounds super happy to talk to me, but I feel bad because hearing his voice makes me miss him more and I want to push him away and it is hard for me not to. I also have in the back of my mind that he left me once and I guess I am afraid he will do it again because we are apart, though he shows no signs of it. He texts me everyday when he can and tells me how much he loves and misses me and how his day is going. I want us to be together and I can tell he is trying really hard. I just don't know how I am supposed to not push him away or think about the break up all the time.