A beautifully written piece of essay, well done! I enjoyed reading it.
I'm not a teacher, I can only pick up a few minor points:
My regular checkups with the doctor were not the most enjoyable moments when I was a child.
When I was a child, my regular visits to the doctor were not the most enjoyable moments.
In the patient room, I felt trapped by the surrounding (austere or some other adjectives?)white walls, the medical posters,(no comma I think) and the obscure(?)instruments. Occasionally I heard a child from the other room, and I knew surely that my time would also come. (The?)Waiting always felt(seemed?) like eternity