When I was 14 I had surgery on my chest for Pectus Excavatum, they removed it when I turned 16 but my left side always felt weirder than the right side. Sometimes it hurts to lift heavy objects or when I stretch my left side.
First I think you need to see a doctor to evaluate what your current problem is and whether there is a relationship to you prior surgery. You did not indicate whether you are still a minor. Contact a local lawyer to see what your legal rights are.
What you should do? See a doctor or physical therapist. We are lawyers, not doctors.
Then don't lift heavy objects.