Worried about everything :/

I had my ultrasound yesterday at 13 weeks. Baby was great, measuring a few days ahead with a steady heartbeat and moving all the time. I would like to just be happy and enjoy the pregnancy, but I cannot stop thinking about two (tiny and stupid) things:

- risk od down syndrome was 1/2400, which I thought was good until I found out my sister had 1/18000 with her daughter. I looked at the data and my papp-a is much lower than hers - only 0.57 mom, which got me worried.

- my placenta is currently covering the birth canal. It is too early to say whether it will cause any issues - it may just come up when the uterus expands, but if it does not it can lead to bleeding and some other complicarion and definitely a c-section.

I know these are not at all serious issues (at least at this point), but with a history of mc I am worried about everything :/

Would appreciate any experience or words of encouragement.

Thank you and healthy pregnancies to you all :))