I can not, for the life of me, understand how this topic developed into such a "My-view-is-the-Right-One-and-yours-is-wrong" discussion. This is a fact: excellent sex is the by-product of a healthy, honest, trusting, encouraging, supportive, and SAFE relationship. If a woman (OR, MAN) is caused to feel that they Must Perform Out of Duty, something is missing. Intimacy - true intimacy - is the prelude to the type of sexual experience that cannot be reproduced via p 0 r n o g r a p h y - it evolves into something that is a mind/body/spiritual experience. And, such experiences make for a healthy, SAFE relationship. The original poster has indicated that she doesn't feel safe, secure, beloved, alluring, respected, or that she can TRUST. Red lights! Warning flags! It's NOT about HER - it's about THEM as a UNIT. Ali, Torrie, silkgirl...you have all hit the proverbial nail on the head and it would behoove the original poster to realize that it's about THEM, not HER, and not HIM. Unless there is domestic violence/abuse going on, it's a failure in the PARTNERSHIP, not either individual.
As I have posted on numerous occasions, a person can experience a sexual release with anyone or anything. And, to the poster who believes that he RETAINS SEMEN in his testicles for months might benefit from an anatomy & physiology course - semen is constantly being replenished, is not stored, and doesn't go stale: it is released through urine, during sleep, in the shower, etc. I knew a woman who's husband would demand (DEMAND) that she attend to his sexual needs on a nightly basis because he complained that his "...balls were heavy..." with semen and that he was uncomfortable in pain - she dutifully would submit to his nightly demands and she felt like a stinking dairy cow by the time she left - the realization that he didn't know his OWN body and had used such a tactic for HIS beneifit altered her view of her own sexuality for years. This whole sexual responsibility thing comes into play: who is responsible for their own sexual activity? The partner? The individual? This isn't rocket science: we are, each and every one of us, responsible for our own behaviors, choices, and consequences and cannot blame our current condition on anyone else BUT our Selves.
If I know that I'm remaining in an abusive relationship for the foolish excuse of "maintaining security," I have ceased being an unwilling particpant and stepped into the role of being a Willing Victim to Abuse because I am CHOOSING to remain, even though I am aware of my victim status. If I choose to have sex with another individual who is not my avowed partner, it is NOT because my partner falls short (!)- it is because I am choosing one thing over another: gratification for ME over emotional intimacy.
It's not the sex that is at issue, here. It is the issues of trust, encouragement, support, communication, self-esteem, and a host of other core issues that are manifesting themselves through sex. Sex is the SYMPTOM, not the core issue(s). Again, I would strongly urge seeking counseling, either individual or joint, to determine what the core issues are, and begin working on them before divorce becomes the only alternative and the baggage full of issues will be carried to the next encounter/relationship.