Many women cannot reach orgasm with penetration alone. Most women need some sorty of clitoral stimulation to reach orgasm. Try buying a vibrator. Wait until no one is home. Light candles and listen to soft music. Relax and remember past sexual experiances. As long as you relax and stimulate your clitoris with the vibrator you should reach orgasm.
Hope this helps.
it's important to relax. especially the first time it is easy to stop yourself just before you reach orgasm because it is overwhelming. take some time to yourself and maybe try positioning your clitoris under the gently running water of the bathtub as you lay down so you can relax and put forth no personal effort... remember to breathe and just let go. after the first time it gets so much easier