I just found out the man I was trying to have a baby with got someone else pregnant?

I'm 23 and I had a miscarriage about 2 years ago (I was 6 months pregnant) and since that time I have wanted a baby so badly...but I told myself to wait for the right man. I recently got engaged and my fiance (who already has a daughter with someone else) suggested that we start trying for a baby. Tonight he texted me, "So I knocked another girl up." And I have been absolutely devastated. I love him, but I'm more hurt that someone else is pregnant with his baby. It's just such an awful betrayal...It goes beyond cheating! Once again I feel like my whole life has been ripped straight out of my hands and there's nothing I can do. Does anyone have any advice?