I've been having chest pain for about 6 months now, it feels like muscle pain but I think it's not. When I exercise or sometimes take a deep breath, it also hurts. So the doctor asked me if the pain in the middle of the chest that lasts for a long time is a sign of what disease? Thank you.

I am a 20 year old female. About 1-2 months ago, I often had pain in the middle of my chest. The first time usually happens early in the morning to wake up or late at night. After receiving the covid vaccine, for about a month now, I have pain sometimes during the day.