He is not going to change. She doesn't see your worth. He is not going to make you a priority. She is going to continue to cheat. You don't matter to him as much as you had hoped and no amount of sex is going to change the status of your relationship.
The guys I know who are happily married have a story about how they met their wives. Most involve a moment when they knew that they needed to spend the rest of their lives with this particular woman in order to be happy.