I have heard of such a thing. I have lived that way. For many years. When H was an active sex addict (unbeknownst to me).
Sexual Addiction is an intimacy disorder. They often cannot be sexual with those they are emotionally close to. They often masturbate excessively and act out secretly sexually with others.
It often develops in childhood or early adolesence as a result of abuse or neglect. What starts out as an unhealthy childhood comfort turns into an addictive obsession. It can also develop from excessive porn exposure, but that line is fuzzy because sometimes the addiction is already in place and the addict becomes addicted to the porn they use to maturbate.
The term that get used for how they behave ith their spouse is sexual aneorexia or sexual aversion.
you can find more info on sexhelp.com. They have questionaires and listings of CSAT (certified sex addiction therapists) by location.
It is an addiction, but it is treatable. Similar to an alcoholic, sobriety can be achieved and healthier coping skills learned. Unlike alcoholism, the SA can learn healthy sexuality and can refrain from addictive behaviors. It is maybe more similar to an eating disorder n that respect, where healthy management of food has to be learned because food, unlike alcohol, cannot be lived without.
This might or might not be your issue. But your post sounded painfully famliar to me.
There can be recovery from SA, and there can be R for the M. Our experience is that it takes longer, but it can be done.BW - Reconciling
edited for typos (I always have to!)