My best friend is now in bootcamp for the military and i think i love him. what do i do?

my best guy friend is now in the military. we had our college life planned out.(well that we were going to go to the same college to say close). any way, he decided to leave and go to san diego. i miss he so much it hurts sometimes. the day before he left me i spent the whole day with him. we never have kissed or said i love you but that day when he dropped me off at my house he hugged me and said he loved me with all his heart and cant wait to see me again. i started crying and he hugged me and sayd "sis" everything will be fine i will write to you and id be like i never left. so i got out of his car and watched him leave. I cried all day. I wrote him a letter and i finally got one back.(he couldnt take his cell they said) and on the letter it said please write me again i love you. But the thing is he calls me sis i dont know if he feels the same. ps he just turned 20 and i just turned 17... thanks guys. ooo btw: he dated my best friends sister. ....