Dear senorita:
I don’t think it is necessary to tell him AGAIN that you were not a virgin when you met him. You already told him once and he chose to not believe it. If you told him that once in a serious way, not in a laughing, making a joke kind a way and he took it as a joke, it may mean he prefers to think of you as a virgin, feeling better that you are in the face of you telling him otherwise.

He prefers to believe you were a virgin. If you can handle it, let it be.

I am not absolutely sure of my advice. There may be other elements to consider, but that is my feel for it.

Oh, and about confessing- are you going to tell him all your past sins, real or imagined? Why? If you believe you and him have what it takes to make a good, healthy relationship, confessing of irrelevant things- like your virginity and many other details- is not necessary and can lead to unecessary complications. Keep it simple.
anita