(Concern) Headache as if hit on the head

I received treatment related to my head last year. I don't even remember how I got injured or anything like that.

My short-term memory has disappeared, you see. Anyway, I received various treatments at that time, but there was no particular problem.

I don't know what exactly is going on, so there's no prevention, and they told me to visit the hospital if symptoms appear during daily life.

Anyway, since then, I've been doing pretty well without any particular problems, but sometimes I feel like someone is tapping my head repeatedly.

There are times when I feel pain in my gut. It's not severe, but since I had a problem there once before, I can't help but be concerned.

It's a bit more concerning because the cause is unknown.

Even after the test, nothing comes out. Why is this happening?