It sounds like there is a lot of issues to be dealt with before you recover your sexuality. Third and fourth party participation in a marriage does not make for fertile ground for healing and growth.
People do all sorts of horrific things because they are in pain, and though it doesn't make it anymore right, it's more understandable than if they are doing terrible things because they enjoy watching others suffer. The motives are moot if people don't use the pain as a catalyst for change. Do you think your H's history of chumming up to the mothers of your offspring is an attempt to purposely hurt you? What do you think he is getting out of these relationships?
I don't mind the sun sometime
The images it shows
I can taste you on my lips
And smell you in my clothes
Cinnamon and Sugar
And softly spoken lies
You never know just how you look
Through someone elses eyes
BHS-"Pepper"