By leaving out the most important part (that you left him and you both dated other people), your post comes across as very biased. Yes, you had a mental illness, but in glossing over your actions, you have not acknowledged how it will have hurt your husband at the time.

From your husband's perspective, you left him and your child and went and saw your ex-fiance. You say that he dated also, but it sounds like you were the first to move on. You can see why he would be very hurt at the time, he didn't know that you had a mental illness, so your "i didn't feel good enough for them" line would have sounded like an excuse to him, especially given how you went back to an ex not long after. I hope you understand why he may have needed to vent to someone like Chris, especially considering at the time that he probably thought you were over.

I'm not saying that you did anything wrong and he did anything right. He definitely should have defended you, but you and other posters have slated him for sharing these details with Chris, and for Chris badmouthing you. Hopefully you might be able to see why it might have happened.