Thanks for your question.
There are a few reasons why you may have vaginal dryness after foreplay--
Changes in hormones. One of the most common causes of vaginal dryness is a decrease in estrogen levels during menopause, perimenopause, after childbirth, or during breastfeeding. (Don't know if any of these apply to you, if not there can still be a hormone imbalance and this can be verified by a doctor)
Medications. Allergy and cold medications containing antihistamines as well as asthma medications can have a drying effect inside the body and cause reduced vaginal lubrication.
Insufficient arousal. In some cases, vaginal dryness may be caused by a low libido or sexual problems with a partner.
Irritants. Some women are allergic to chemicals in soaps, hygiene products, dyes, and perfumes.
Anxiety. Psychological and emotional factors such as stress and anxiety can also wreak havoc on sexual desire and lead to vaginal dryness when normal vaginal lubrication does not occur.
Treatment for dryness will depend on the cause-- if it is hormonal, then your doctor may treat you for that. But for all other reasons you can buy an over the counter lubricant or moisturizer to make sex more pleasurable and less uncomfortable.
Hope this helps!