First time relationship help?

im more practical... he shows me how much i mean to him like all the time but im more secretive in the sense that i wont say how i feel n stuff all the time but it doesnt mean that i dont feel that way. uhm we've bn arguing alot lately about it... he wants me to show him and say how i feel and in his words, "act like his girlfriend and not a stranger". how do i make it up to him and start to be like that. it's difficult for me cuz i tend to feel vunerable bcuz of my past but im willing to try i jus dont kno how...