help with relationship!!

so i'm 15 and have been dating this guy for like 3 months now. we're both comfortable around each other, but i'm scared to kiss him. a month in the relationship he went in to make out with me and i pulled away because i was so nervous and couldn't even move my lips and then did it a second time too so now he just doesn't try. except for when we are getting ready to go and he gives me a peck on the lips. i'm really attracted to him and i want to kiss him but i always get really nervous because he's made out with people before and i haven't. it makes me so upset that can't just kiss him considering we've been together a couple months. advice please!!