At what moment did you first notice that your hair was thinning?

I only realized that the top of my head looks thinner than before after taking a photo recently.

I usually only see my front in the mirror, so I had no idea.

Even when I tie my hair up, it seems to have less volume than before, so it's starting to bother me a little.

It seems too early to conclude that it is hair loss, but
I would like to hear from those of you who have experienced female hair loss about what changes first made you notice it.