Answer: I am guessing that you have been taught by your parents that touching your genitals is bad. You may have learned this as an infant. The people around you may have reinforced this, when you were very young.
Undress in front a mirror; a large one that allows you to see your entire body, if possible. Print out the following and tape it to the mirror in front of you. Then read, out loud if possible, what is written.
"This is my body."
"I have the right to enjoy my body."
"My body can give me pleasure."
"Pleasure is good."
"I have the right to give myself pleasure."
"My body and pleasure are good."
"I want to give myself pleasure."
"I am going to give myself pleasure.
Do this several times prior to masturbating. If you are home alone, say these things out loud and in a loud voice. While riding the bus to school or any time you have a spare moment, repeat these things to yourself.
Get a handheld mirror and examine your vulva closely. Identify all your different parts. Get some lubricant and slowly and gently massage it into your genitals. Discover what feels good. Remember to stay relaxed and breath.
Continue to rub your vulva against a pillow, this practice is a form of outercourse. Go slow, stay relaxed, and breathe. Move your hips slowly and experiment with different pressures. Try wearing different cloths, types of fabrics, and totally nude; this will change the type of stimulation you experience.
When you shower or bath, take a couple extra minutes to explore and caress your vulva each time.
Do not try to have an orgasm. If one happens, it should be a surprise. If you try to have an orgasm, it is less likely to happen.
I suspect you are not the only girl in your peer group, or group of friends, who has not learned how to masturbate to orgasm. They may say they have, even if they have not, because they do not feel comfortable admitting it, especially in a group environment.
The following articles may also be of help.
Perception of Sexual Arousal and Desire
You can also learn from the experiences that your peers have shared with us.
The Body Image section of the website may help you feel more comfortable with your body.