In need of some advice!!!!

i was with my ex for 9 years and we have two kids together. We broke up a year ago and he's currently in a relationship with someone else. He immediately started a relationship with this girl no sooner after our breakup. The girl now has a baby with him. We have been sleeping with eachother the whole time. I know it's wrong but feelings don't just go away over night. He cheated on me with her and now he's doing the same to her. He is there anytime I need him for anything. I've never met this girl and he makes sure we never come face to face with one another. He doesn't bring her to anything of my kids sports / bday parties nothing at all if going to be there. I feel bad for her but how dumb can you possibly be? He made it clear that he didn't even want the baby that she had and she still had it. I'm so confused and it's so hard to leave him alone as I tried several times ! What would you do ?

Either you're with him or not. You have basically assisted him to betray the other woman and how can you feel bad for her if you call her dumb? You're in no position to judge anyone without first resolving your own issues with your ex. If you need to be with your ex, then do it properly, if you don't, then do it properly also and that means the only connection you should have with him it that he is the father of your two children. While you both continue to see each other behind her back, you are helping to create a no win situation which will come back to bite you big time. If you know it's wrong, then you should know that if you do something wrong long enough, you will always get caught in the end. You're correct, feelings don't go away overnight, but they never go away if you continue to maintain them whether it's right or not. Think of your children and be true to yourself and do the right thing by yourself.