Well since firstly the pain responded to Advil
and as you mentioned that whole investigations could not lead to any diagnosis , it could be of muscular origin. You need to get in touch with physician and get a CXR
- PA view,ECG to rule out any chest or cardio related problem . You should carefully watch out for symptoms if any like coughing , fatigue
, sweating , palpitations etc and take prompt action if any of these appear . It is not advisable to take Advil on daily basis for prolonged periods
because of its side effects. You can take it if pain is there but need to be in regular contact with the doctor who prescribed it .
Thanks for reference.
Get well soon.
Dr. Shruti .