I just saw this on PostSecret.com.
This is a real issue that seems to get very little attention. Just because you are married does not mean you are obligated to have sex if you do not want to. If a spouse coerces you, forces you, gives you a guilt trip until you reluctantly give in, threatens you, says you do not love them unless you have sex with them, etc- it is rape and exploitation. Your body is your own, and no one owns it. Marriage is not a property right.