I would disconnect myself from both of them. Depending on what you think or know that they are doing....and if this has happen a lot of times before. To be unfaithful would only take one time for me. The trust is gone. All words are not believable. All plans have no hope......and the flower have turn brown. It is best to nip-it-in-the-bud and end the matter or it will be a long road to a simple solution. The thought that it can still work out don't hold any water.It will only get worse if you remain together.
And 75% of the burden will be on you. It will always be mayhem in the AM...and the PM hold no thoughts of comfort.