Why is my boyfriend so over Emotional?

I've been going out with this guy I like for only four days , two of those days I didn't see him. But when as soon as I go on facebook he starts talking to me, asking me questions which I don't mind, he's always giving compliments, whenever I post somethng on some other guys wall or comment on their status/picture he gets really protective of me and tells them to leave me alone and then it gets into an argument. But then the next minute he is completely carmed done and he is telling me he loves me, saying he is so lucky to have me, telling me that I'm beautiful. I didn't mind at first but It's getting kinda annoying. I always have this problem with guys, they either ignore me or act really creepy around me. I love him, infact I liked him before he liked me, he even asked my friend out first, which nobody can understand why. Help , thank you