your reaction to the "problem" could be perpetuating the problem. stress, such as anxiety when thinking something is wrong, can significantly increase or decrease the time it takes to orgasm. if it bothers you too much, maybe masturbate once a few minutes before you and your partner get intimate. otherwise, just relax, go with the flow and if the first time wasn't enough go at it again when you recover from the first time. basically, it's not a problem really, don't fret it