Sexual Intimacy and Sexual Trauma in Marriage

If sex is an indispensable part of a healthy marital relationship – what does this imply for a marriage in which the act of sex has become traumatic for the wife? That's my situation. There are a couple of reasons for this, and neither of them has anything to do with past abuse or a history of negative sexual experiences. It's partly a question of pain and discomfort due to physical issues, but the bigger problem is my emotional revulsion to the perverse sexual practices in which my husband wants me to engage. He's been addicted to pornography for at least a decade and half (only recently discovered), and he's constantly asking me to help him act out the disgusting images he sees in magazines and on the Internet. As a dutiful wife, I've tried to maintain a "healthy Christian marriage" by accommodating his requests. Unfortunately, it's only made things worse. This leads me to wonder: can sex actually become a barrier to a healthy marriage when it can't be expressed in the way God intended?