it is so amazing how much alike we are in how we feel about exes. I posted on yours because it is exactly how i feel about ex and his GF. My ex has introduced her to all his family members and it [censored]. I'm jealous because I can see them getting married and I feel like she has taken my place. On the other hand I like you I still wouldn't get back with him and I would like him to be remorseful but I have drawn a line on it. It will never happen. I need to make peace with it. I think we still have feelings because we were still in love with exes and we didn't pull the rug under our feet (they did). I also believe that with time these feelings will fade away.
You are an amazing mother and your child will realise who has been there for him all the time.