Hi,
This might have something to do with your hormone levels, or your age. It's not uncommon for some women in their 40's to start noticing decreases in sensitivity and pleasurable sensations because of approaching perimenopause or menopause. Another reason could be a natural drop in hormone levels (progesterone, estrogen, and testosterone decreasing) that can sometimes cause a hormonal imbalance ~ which has a direct affect on sexual arousal and pleasure. You could speak with your doctor about this sudden loss of feeling, and you can also research 'Sexual Side Effects of Perimenopause'. If you think this could be perimenopause/menopause, there are also herbal remedies that may help increase your sensitivity and sexual response; talk w/your doctor about treatment options. For more idea's to research natural options for supplements, you might want to check out: Ashwaganda Root, Maca Root, Muira Puama, and Dark Chocolate...
Good Luck :)