Hello,
Thank you for asking at HC magic.
If chest Xray and ECG is normal than it is very unlikely to be a problem with the lungs or the heart.
1. The next needed exam that I would recommend is an abdominal
ultrasound. It will check your liver, kidneys,
spleen and
pancreas for any lesions
2. If the ultrasound comes out normal than it is very likely it is a
muscular pain and I would recommend you to have
Tylenol regularly to help with pain.
3. Bowel might be a cause of pain in left upper quadrant also so if you are constipated (have rare bowel movement or difficult ones) than make sure you get extra fiber in your diet and drink plenty. Make sure you have frequent small meals and avoid fatty food or fried food (junk food also)
4. Local warm compresses at the area might help with pain also.
5. In muscular pain there are exercises that can be made that help muscles relax and release pain so a physiotherapist might help also.
6. If no improvement with these or any worsening you will need to see your doctor.
Hope this is helpful and answers to your question.
Best Regards