Kinda embarring... But hey I need help from experienced girls! ?

Okk so I've been dating my bf for 6+ months now and we've done most things except I'm to scared to give him a *******. I'm scared to death that idk what to do cuz it's true! I've never done it before so I really don't know what to do! When we do stuff and he's about to "finish" hes always asking me what I want to do with it... And I say idk what do u want to do with it. And his answer every time is you know what I want. Given the fact that I'm 17 I feel really bad because I wont do it. I feel like I'm being childish. But it's just the fact that idk what to do. So can you girls who have done this before help me?! Tell me basically what to do so I have an idea?!?! Please! And any reuring would be welcomed. No mean answers please. Thanks