Unlike the great majority of men, women are theoretically capable of experiencing multiple orgasms with sufficient sexual stimulation. However, it has been estimated that only 25% of women experience orgasm with penetrative sex alone, with many others requiring additional clitoral stimulation. As many as 12% never attain orgasm, this being known as anorgasmia.
This does not stop sex from being enjoyable or pleasurable, and lack of orgasm is only a problem if the woman feels it to be so.
Physical causes of anorgasmia can include hormonal imbalance resulting in a lack of arousal, or insufficient engorgement of the female genitalia in arousal to provide lubrication or increase sensitivity to stimulation. As in men, the equivalent being erection, this may be the result of other conditions such as vascular disease or the impairment of the nervous system for various reasons.
Lack of lubrication and changes to the lining of the vagina can result from the menopause. Psychological factors which prevent the development of arousal or the experience of orgasm can be numerous too, and these are outlined in more detail under the Arousal section of this web site.
The physical causes may be responsive to treatment. Use of a simple, water-based lubricant might be sufficient to remedy the situation. There have even been trials of Viagra in women with some indication that it can aid in the female equivalent of erection, but there are many more factors to be taken into account with regard to women than men, before the prescription of such a medication is likely to be considered. Non-physical causes may be successfully treated with counselling or therapy.
You should not be embarrassed to talk with your doctor about inability to attain orgasm, especially if this is a new development. Sexual dysfunction can occasionally be an indicator of a more serious condition which is more easily treated if found early.