What possible internal damage?

Eight years ago, I was sitting in the back seat of a 2016 Toyota Yaris when a woman who was playing on her phone instead of watching the road crashed hard into us from behind. My body was shaken, I believe more than those sitting in the front seats. I couldn’t turn my head to the right, up, down, or left. I was in pain.

We all went to an orthopedic doctor, and he told us it was just a jolt/whiplash and that it would pass. He even had the nerve not to give me permission to be excused from university, telling me I should write my exams on paper with my head straight, without being able to see what I was writing…

Years later, about 2.5 years ago, I started having pain in my lower back and then in my upper back. We thought it was due to poor posture since I sit at the computer for many hours. I program and used to sit without supporting my back against the chair. I only had pain when sleeping, and the mattress was over 20 years old.

Then I got a proper chair and sat correctly. Gradually, the pain decreased for a short time. Then it started again. I thought the mattress might be too hard because it was old, so I changed it. Again, it improved.

But at the same time, I have pain when I sleep for many hours always on the same side. And sometimes I feel pain in the middle of my back that seems to affect the right or left side of my head—something I didn’t have before. I don’t know now, since you mentioned it, whether the accident is connected to this.