Question about co-parenting

Does anyone have any advice on how to co-parent with the ex? Does anyone have any stories about their children being around and meeting the "step-mom"? This is killing me. Not only did he marry after 6 weeks, but my child now has a stepmom and about to have a 1/2 brother/sister in 9 months. Is this the normal thing today? I was sent to catholic grammar school and high school, and I never thought I would end up with a life like this. My ex just dropped of our son, and I am sitting here crying because my son said he played with the ex's wife this weekend. ughhhh ;-(
I pray to god everyday for strength. I don't know how much more I can handle.