"Some women may have an iron deficiency, and the first trigger is that they don't want to have sex." You're in pain. shambhalafundacion.org When sex doesn't feel good, your desire takes a serious hit Estimated Reading Time: 7 mins. Many women in long-term relationships also lose interest in sex because they don't want the kind of sex they've been having. "When two people have been together for a long time, sex often gets routine and stops feeling personal," says Ruth Morehouse, Ph.D., co-director of the Marriage & Family Health Center in Evergreen, Colorado. There may be other reasons why women stop wanting sex, but here's the top 10 (including some you haven't thought about.) 1. She's unable to orgasm (or orgasms infrequently) Only a third of all.