So scared of not having a healthy pregnancy

My last pregnancy completely scarred me. I miscarried at 13 weeks. Genetic testing showed that my baby was at high risk for trisomy 13/18. I am so terrified for something to go wrong and I am still SO early. Only 4 weeks and 2 days. I'm literally losing my mind! I can't relax about it. I'm only 21 and I was at risk for someone who was 40, I couldn't believe it. I don't know if it was sheer bad luck or if it's because my boyfriend and I just aren't compatible to have a baby? I have so many questions and concerns and I couldn't get a doctor appointment until the beginning of May, because I'll be 8 weeks then.