Should I ask him out or should I wait?

Hey my ex and I broke up about a month ago. We still flirt and all and act like were still together. We talk and he even says mwah (kiss) before we end the conversation. His twin sister said that he would say yes if I asked him out and I really want to do it now. I have already text him 3 days in a row saying hi and he said that he would text me when he usually doesn't. Should I do it now or wait until he texts me?