Anyone know what book I can’t think of the name of?

I can’t remember the name or author I read it a while back, and I read alot. The main character woman was married in a loveless verbal abusive marriage to a narc. She ends up desiring cheating (I can’t remember if with a woman or a man, she was bisexual) and they had a child together I think? Or maybe it wasn’t there and was a niece / nephew. Thank u