I understand your feelings, I sometimes think the same too...
But I talked to my husband, he asked me not to scare myself. If there's no pain, no bleeding, then no need to worry. Otherwise, you will be worrying all the time during your whole pregnancy. We can't do u/s all the time. Well, by telling you, I think I'm telling myself the same thing too...
I also have the same worry before
but no more worry after my husband told me he can hear our little baby's heart beat from my belly yesterday
and he said the sound of it's heart beat is very fast and strong
so you can try to do that tonight with your husband