Hi, I Am 16 Years Old And I Go To

Hi, I am 16 years old and I go to school in Canada. Yesterday, I decided to go to the weight room at my school in the morning, and I forgot to have my breakfast but I still exercised anyways. After, I had a bite of a sandwich that I got from the school's breakfast program but I didn't finish it because I had no time. About an hour and a half later (after first period) I went to my Phys Ed class and we had to do a 15 minute run around the gym. I was already tired from this morning, but I still decided to go on. After the run, I was tired, and after we continued to play a tennis-ish kind of game with balls and rackets. When I tried to go for the ball, I dove and hit the side of my head. It only hurt for a while after but my teacher gave me a "possibility of a concussion form" to give to a doctor to sign this weekend. I went to a walk-in clinic and told him only the part of the story where I hit my head and he asked me for any symptoms and checked my well-being. He said I had no symptoms or signs of a concussion but he said that since I still hit my head, I have a concussion. I am skeptical, and I am considering seeing another doctor. What do you think?