Answer: The thing to keep in mind is that even if you did not ejaculate for an hour during vaginal intercourse, your girlfriend probably would not have an orgasm. She may not enjoy vaginal stimulation no matter what you do. The majority of women require clitoral stimulation if they are to experience orgasm. If you are concerned about giving your girlfriend pleasure, then orally or manually stimulate her vulva and clitoris to orgasm prior to intercourse. Make sure you take care of her needs before your own, as least on occasion.
Your ejaculating so soon is only a problem if that is all you do with your partner. If sex is over after you have had your orgasm, then it is a problem.
Tell your girlfriend what you told me concerning why you do ejaculate so soon. I am sure she would like to know why, so she is not left guessing.
If she wants to experience more vaginal stimulation, use your fingers. Make sure your fingernails are trimmed and smooth, and that they and your hands are clean. Then, starting with one finger, caress and massage her vaginal walls. Do not just thrust in and out. When her vagina relaxes and opens, switch to two fingers, and so on. Doing this will help relax her pelvic muscles so that she will not be so tight. Help her to learn how to do Kegel Exercises.
Buy some water-based lubricant and use condom(s) to decrease the sensitivity of your penis during intercourse. Masturbate to orgasm "together" before you have intercourse to help relieve some of the sexual excitement.
Finally, do not make the sole reason or purpose of sex vaginal intercourse. On occasion, make her the center of attention. Focus on her sexual pleasure.
Webmaster's Note: I'm not a supporter of the concept of "premature ejaculation," as it is simply too common an experience to be considered "abnormal". From a reproductive perspective, there is a benefit to ejaculating quickly. I also believe society places far too much emphasis on sexual intercourse, even though women frequently don't experience orgasm during the activity.