Left chest & shoulder bla. To visit?

My mom is suffering from acute pain in chest area between the lungs which spreads out to the shoulder blade and some times to left breast.We consulted Gastroenterologist.He suggested ECG and ultrasound scanning.ECG is normal and the doctor ruled out Heart  and  fastric problem.He prescribed some tablets related to gastric problem.But still the pain won't  go away.So we visited general physician.He prescribed some pain killers for 3days.Her condition improves when painkiller is injected but pain comes back normally after 12-14 hrs. I'm completely confused about her condition and clueless as to visit which doctor.I searched on the internet and found out that the condition could be Costochondritis or pericarditis.So please suggest me which specialist to visit? A pulmonologist or orthopedist or cardiologist or rheumatoid specialist. Thank you