You have three tasks to do at the same time.
1, let the man know that you already know that he has a mistress, and you care and object. You must be tough on this.
2. You should let men know your gentle side. Who doesn't like a gentle and virtuous woman who knows books and is polite? Remind him of your happy time together from time to time.
3. Find a mistress and be polite first. Ask him out for coffee first and ask him to quit during the conversation. If she doesn't eat hard, you can find some hooligans and fuck her behind her back. But you should be careful not to make a mess of things.
The above three moves have been practiced for a month. If he still fails and the man still doesn't change his mind, then the last resort is to dump him. This heartless man, don't let it be!