Dear sir , I'm very sorry to hear your suffering. It must be hard for you to even come into terms with what has happened between you two so as to reach this. But It is important to believe the first logical step is for both of you to agree to each other that things are not same anymore even before confronting. You are going through a difficult period of low mood and anger which is a normal reaction when your are trying to adjust to a distressing reality. So please as a first step don't put any thoughts in your mind which serves no realistic solution now.
Next Steps
It's important to confront you're partner confidentially with proof of how you came to conclusion, this will automatically move things in a direction that finds a suitable resolution for both. You can use a marital counselor for helping you to facilitate the entire process . But if this adjustment phase is long enough to spoil your role function , sleep and appetite, then please do consult a Psychiatrist who will guide you holistically with realistic solutions. Take care.