I battle this from time to time. It started when I was in my 20's. It is very painful. It is inflammation in the breast bone. You are sore in your breastbone and it hurts much. The doctor did no x-rays of me either. My mom had it and it tends to be hereditary.

I was told to take Advil (I can no longer take Advil) for it and rest.

I had a dear friend who thought it was her heart. She had just taken up swimming in her late 70's and low and behold the swimming brought on the Costochondritis.

Praying for relief for you. Blessings.

I had a flare after COVID and all that coughing with pnemonia & bronchitis set it off. It takes a while for it to calm down.