Confront your partner about what you know. Set boundaries, state what you are willing to accept and not. Do not give ultimatums unless you mean them. Remember that it is very rare for affair partners to marry one another. See if you can work things out first.
It is important that you confront your partner once you find out about an affair as soon as you realize it is happening. Colluding to allow the affair to continue while you gather more evidence will not work. It is best to present the evidence that you have and see what your partner says.
It is not advisable to contact your partners’ affair partner because you want to avoid more damage to the trust in the relationship. Remember that most marriages and long term partnerships survive infidelity. In order to preserve the trust it is better to deal directly with your spouse.
Serial cheating can be an indication of an addiction or compulsion to seek sex, love or romance. Serial cheaters feel driven to seek out affairs and sex when feelings of anxiety and are urged to be filled. They get a thrill by seeking the encounter and become filled shame and worthlessness afterwards. They try and try to quit but can’t. They are acting outside of their values and will tell you so. The key identifying factor is that the affair is used to avoid other emotions.
Serial cheaters can also have personality disorders. The identifying factor is they have no empathy for what they have done or remorse. They are impulsive, shallow, superficial, grandiose with a lot of charisma and black and white thinking. The best course is to seek help from a mental health professional.
Porn is highly addictive. Most people who use porn a lot experience sexual performance problems, causes isolation and reduces self esteem of those who use it. If he is not participating in family life then set your boundaries about what you will and will not live with.
Usually people engaged in this type of behavior have the belief system that their partner is not “getting enough at home”. Although this is a common occurrence as a way to get reassurance it is not helpful because it can feel violating to both parties and add to an already chaotic situation. It is best to act in accordance with yourself and your beliefs rather than try to manipulate your partner back.
Get support from trusted friends who will NOT bad mouth your partner to others or spread rumors. Find a friend of the relationship who is supportive, empathetic and objective. Warning: It is best not to involve family members and children because they may hold a grudge long after you have healed.