If my boyfriend goes abroad to study, so far...and i'm jealous much, how can i keep my love ?

bz he is far away from me( he's in US , and i am in VietNam, he goes abroad to study ) i 'm afraid of I can't keep going my love as the past time bz i recognize that i'm jealous much and i 'm afraid he may be have another girl . Some day near, i saw that he was strange in talking with me ,maybe i think so much bz we are just keep in touch by chatting . How can i keep and refresh my love ? what should i do now ? break or keep going . If he didn't reply my email as he promised and he seemed not to interested in talking with me as in the past time when we were togther ( in Viet Nam ) , Does he change his love ? Does he p me in the silence ?