Affair as I needed sex

Been married 16 years, together 18 years. Husband literally stopped sex with me when our daughter was born. I should add I am 20 years younger than him, attractive, and a professional. He is a workaholic, but works nearly all from home, does not travel, is a good father and provider. For 14 years I just accepted it. NEVER dreamed of straying. He is NOT having an affair, and has/ had a lot of serious medical issues so can’t even have sex any longer. He is perfectly content it seems to just live life as if this is a healthy marriage. I have been seeing a single dad for two years now, and the sex is good. I get away when I can, and we see each other during the week due to our kids’ mutual activities at school etc. He wants to be together all the time. I am content I guess getting sex and attention from him, and staying married. Maybe my husband knows, but he is the type of person who would rather keep up appearances so never hints at anything. We do not sleep together but have had separate rooms for years. Anyone else in this position, where they want regular sex and cannot get it from a spouse but otherwise are complacent about staying married? I cannot see how financially divorce makes any sense. And yes, I complained for YEARS about him not touching me or being romantic after our child was born. I am in great shape and always was, so not like I let myself go after the baby. I just believe he is and was very embarrassed about his impotence and stopped trying. Thank you for whatever input you have, and it is fine to slam me for being unfaithful to him! I have asked if we should just divorce and he told me that “would be selfish and cruel” to our child. I truly wish he would DIVORCE me!