You are not worked up enough. Try some foreplay and take your time and you'll enjoy every minute of it. How old are you and where you from?
Why Doesnt My Vagina Get Wet During Sex?
Birth control is known to stop sex drive so if you are on that, that could possibly be one of the reasons. Also you need to try foreplay. Stimulate yourself and get your body worked up until you feel wet. Then start the intercourse.
Are you on any medication? That could cause dryness. Otherwise, it sounds like you aren't really turned on. Try and get your partner to spend more time on foreplay, or just playing in general. If you're over anxious about sex, that could dry you up.