Miscarriage at 12 weeks

I went in for my 12 week ultrasound to find no heartbeat. Devastated. I am now waiting for my D&E appt in 2 days but struggling. My Harmony results came back that the baby had Down's syndrome which is likely the cause of the miscarriage but I'm only 34 and have one healthy child. Now I am scared to even try again. I'm scared of the whole miscarriage process, which hasn't started yet. I'm just scared.