I like my substitute teacher so much! how can i do?

can anybody help me to figure it out? i like my subtitute teacher so much! we met 4 times in classe and i started to like him from the 2nd time i met him! then i added him on facebook but he didnt accepted me. but at 4th time he met me and he was talking to me like usually then i asked him why didnt he accepte me on facebook? he answered me'' im pleased to talk to u but the thing is a teacher cant be a friend with a student if not i can lose my jod'' i really dont understand! that mean he also like me or interest in me but just he cant bcuz he have to pay by his job? that what he mean? he's 21-24 sth! and im 17! i dont know why i feel like i like him so much and it happend to me 3 months already and everyday i feel like im dying! i wanna see him, talk to him!