There can be a number of reasons why your lubrication vanishes — you say you start out wet, then dry up. These can be physical (for instance after childbirth, due to hormonal changes) They can also be emotional. Are you staying excited? Or, do you lose your desire part way through? Do you kiss, caress, a lot or is it just intercourse? Are you distracted by thoughts? Does your husband help you to have an orgasm with external stimulation (eg oral sex or manual clitoral stimulation) before intercourse? Read this article on women and orgasm to give you some tips: "Freeing Female Orgasm". We also have a detailed ebook "Awakening Women's Orgasm".
 

Also, lots of sex educators recommend using lubricants during intercourse. It helps to keep things smooth and slippery for both of you. During extended intercourse, with lots of friction of penis on vagina, it's common for some dryness to set in.
 

Good For Her, a fabulous women's sex store and education center says: "Lubricants are a must! Whether you are looking to increase the slippery slide of sex or masturbation or to relieve vaginal dryness due to menopause, aging, childbirth, medical conditions or other factors - lubes are here to save the day. From underwater adventures to increasing everyday slick sensations, lubricants can make good sex great, and great sex out of this world!"

Some good lubricants are made by; Astroglide, BodyWise, BioGlide, Hathor, JO Women.