What's the difference between infatuated and love?? more details?

My gf and I are so happy together it almost doesn't seem real! We can be totally honest with each other and everything seems to go so right. I feel like i would protect her from anything or maybe even take a bullet for her. I don't know this feeling i have it is just so unbearable but i don't think i could live without it is it love or infatuation??? please help she means the world to me but i don't want to tell her i love her if i don't know what "love" is