A lot of women have trouble getting orgasm while hving sex. It is just harder for some of us. If she knows how to make it work that is good. Some women never have that. My grandmother never had one her whole life. It is not you, some of us are just too sensitive and if we dont get it right away then we are overworked, if you know what I mean. Others are not sensitive enough and if proper pressure is not applied at the right time we cant get it either. It is not you believe me.

She's probably using your member to stimulate her clit, the part that needs to be stimulated for her to get an orgasm. I know this is the only way I can climax too. If you want her to go while you are inside of her, you should try rubbing her clit with your hand while you are thrusting.