pregnant with twins, boyfriend just walks out

Me and my "boyfriend" have been together 6 years. We have been wanting to have kids with each other. Well Monday I found out I was pregnant with twins. He ended up leaving me and said we can be good parents to them and give them what they need but we don't need to be together anymore. Seriously?! Who walks out on someone you've been with 6 years AND is pregnant with YOUR twins?! There was no explanation or nothing!! He said he wasn't ready for a relationship. ARE YOU KIDDING ME! We were a relationship for 6 years and talked about marriage and talked about having kids in which now we are!! What do I do?! I'm lost for words. This is my second pregnancy, first ending in a misscariage, but I honestly have no idea what to do to get him to stay or change his mind!!