I love a guy who left to the military without knowing...

We were in high school when we met. he was open about his feelings towards me, and he even “swore it on the bible” to mine and his friends when i wasn’t there. the problem was that he always flirted with other girls IN MY FACE and i didn’t like that, and besides the fact that i was in a relationship, i wasn’t going to give him a chance. However, as time went by, and the flirting continued, I began developing feelings for him. When my boyfriend and I broke up, he asked me out.. to his house. I didn’t know what his intentions were, so I cancelled. He was really upset but what really pissed him off is that I was back with my boyfriend a week later. After that, he completely stopped talking to me. He then joined the marines, and a week before he left he called to say goodbye. Its been 4 months, and I constantly dream of him coming back and living our “happily ever after” and I think of him often, all the songs we used to listen to and the stupid things we would do. I don’t know how to correspond to my feelings. I am still in the same relationship with my boyfriend, so also, I wouldn’t want to hurt him. What should I do???