My bf is nervous about kissing me?

ino this sounds like a 12 yrs olds prob, bt im honestly 16, nd hes 18. nd wev just got together but he is really really worried about kissing me. hes never had a gf b4, or kissed any1 (no funny comments please) bt iv had 1 bf b4. so i said i wud kiss him, bt nw hes saying he dusnt know if he wud kiss me bk. so i got abit upset nd wondered if he found me unattractive or something, bt he says he does find me attractive nd itz nt tht, hez jst really awkward abot it, bt i will b mortified if i try 2 kiss him and he doesnt respond. i mean i am his gf, y does he nt want me 2 kiss him? also hez 6ft nd im only 5'3 so any suggestions on how i shud go abot this will b greatly appreciated.