I am direct blunt person(as people here may say) so please do not think I have no compassion for your situation. But...If you are the cheater or the... cheat-ee, you can expect either person to remain faithful. One person might be able to be the other man, or woman aka the cheat-ee and then remain faithful but you are dealing with someone who is already married or in a relationship. Expecting faithfulness under those circumstances is a bit...naive? and on the flip side you were involved with a married woman and had been cheated on before. what does that say about your moral code. And listen I am not picking on you and I dont think you are a sh**ty person. You were hurt by a woman in the past, you have PTSD you're a vet(thank you for your service) so you have some baggage to lug around. I think an absolute clean break ( other than child issues) and a nearly no-contact relationship(other than about the child) will help you heal.