Mary1389 is right. Your boyfriend has very little to no experience with romantic attention and sexual expression (which doesn’t have to mean full on sex — it can mean kissing). He’s scared of his feelings. He’s scared of your feelings. He’s scared of messing up his relationship with you. He’s scared of making a wrong move. And he’s scared of making a right move and not wanting to stop.
Being a teenager and exploring sexuality and romance can be wonderful — and frightening. He’s not wrong for having these feelings, and neither are you for having yours. You’re both at different stages (as are most people regardless of their ages), and your relationship calls for communication and understanding and empathy.
My advice to you is to dial up your empathy and dial down your aggression. Let HIM be the one who grabs your hand — even if it means having to wait for him to do so. Let HIM be the one who gets close to you even if it takes a while for him to do so. If you give him control of the expressions of affection and sexuality, he may have less fear and eventually more confidence.
Hang in there!