What you describe is going from arousal to "resolution," without experiencing what you used to as orgasm in between.
The first thing I'd check if you came to my office is whether you're on any medications that could interfere with orgasm. The biggest class of medications in this category are the SSRIs—antidepressants like Prozac and Zoloft. If you are, you can talk to your health care provider about alternatives that would have the effects you need without the same side effects.
Difficulty with arousal and orgasm are more common as our hormones change through menopause. The loss of estrogen diminishes blood supply to the genitals, which affects sexual response. There are a few ways to counter that loss:
One more thing to consider: Women have at 50 about half the testosterone she had at 25, and testosterone plays a critical role in libido and ability to orgasm. There's no FDA-approved product for women, unfortunately, but I prescribe testosterone off-label for patients with good results. Off-label use of Viagra or Cialis is also helpful to a few women. All of these off-label prescriptions require a conversation with your health care provider—and consideration of your overall health.
There's every reason to be optimistic about regaining satisfying orgasm!