Chances of a missed misscarriage

I wish I could stop being so worried. 2 of my friends have had mmc

And reading on net I'm so worried I'll end up in the percentage too.

I had a scan at 7 weeks 2 days the nurse said everything looked fine baby had a good heartbeat.

Since 8 weeks I've been so exhausted and constantly nauseous but luckily only been sick 3 times.

My breast haven't grown at all which worrys me. Sometimes they're sore but most of time nothing. My nipples are slightly sore.

I am 10 weeks today and woke up not feeling sick at all. I am still exhausted and my nipples are still sore.

But reading online you can have a mmc and still have symptoms.

So my question really is what's chance after seeing a heartbeat. I'm petrified for my 12 week scan