What Causes Dryness In The Vagina?

i am married (26/04/2001) earlier i have satisfied 2 girls for many months but when i got married & tried it with wife she complained about vaginal dryness & she ejaculate late. i am normal because after marriage i was satisfying a married women for nearly 15-20 times this was when my wife had gone for delivering my baby.
how to overcome the problem of wife?