I'm trying everything

My finance and I really want a baby. He has a daughter I have a son. We want to make our family complete. What else can I do? I conceived in May and had a miscarriage at 6 weeks :/ idk why:( I follow the fertility chart. I try to eat decent. I cut back on alcohol a lot. I had 1 beer yesterday... That's good. I do smoke I'm slowing down a lot. Any advice :(