Same same, when my daughter was about 3 had blood in her stool, that time we took her to the hospital and she spent some days there with my wife. It was nothing, never happened again.

Another time she started screaming and said she had pain in her stomach, it was one of those scary screams when you know something is wrong, I was driving as fast as possible but encountered traffic and heard her laugh on the backseat. I guess it was just gas or something, we went back home.

And finally she fell playing in a floor fountain and opened her chin, the wound bled a lot and we took her to emergency, while waiting she forgot she was injured and started playing and jumping while waiting.

What I wanted to share with these stories is: humans are delicate but resilient. What OP is feeling is normal and I had exactly the same doubts. But with time you get the experience and you start “know” when something is wrong.