Does your SO feel confident about his penis?

My SO is extremely shy when it comes to his penis! I love him and he has pleased me above all others!! I tell him over an over how much I love making love to him and that he's the only man to make me cum vaginally but he still folds into insecurity and i don't know what else to do or say to make him feel confident enough to slap that peter in my face or butt or anything what can I do to make him feel more secure other than telling him its big or that he pleases me because i believe he think I'm lying! I also think he believes im much more experienced than him! Please any advice on how to make him feel at home in my vagina????