My ex and I dated on and off for 8 years. A little over 2 years ago we had a son and started living together. Things weren't great, but they were OK. A couple of months ago, I found out that he had been sleeping with this girl who was 4 years younger than me for the past two years! I was shocked to say the least! Not to mention that when he got caught in his lies, he went back and forth between us trying to mend things on both ends. Needless to say, I moved out and tried to get on with my life. Since then, him and this girl are still together and he still tells me he loves me and wants us to be together. He's such a manipulating liar, I can hardly stand him at most times. I don't want us to be the kind of parents who absolutely can't stand each other but I don't want us to be best friends either. How do I let go of all of this and have a platonic relationship so my son isn't the one who suffers in the end?