cant climax during sex

Thiss normally happens when your tense, try to relax and really get into the mood before he enters you, do you orgasam a all druing sex or only when your alone... may be a bit of clitrol stimulation can help you on the way to a vaginal orgasam, also it seems you focus alot on your partner, try to focus on your self a bit more.
I hope some of this helps you out let us know how you get on :)