Hello,Customer Your sore chest muscles could be caused by something minor such as muscle strain; however, since you have a recent history of "partial lung collapse" (pneumothorax) and since you have a symptom of sore chest muscles every morning when you wake up after lying supine in bed and your chest pain goes away after you are standing upright, then this could be a sign that you have a "recurrent" pneumothorax. I advise you to return to your physician who treated you for your previous partial lung collapse and have him examine and treat you for a recurrent pneumothorax. At the very least, you should have a chest X-ray. You may require a thoracoscopy with pleural abrasion to prevent recurrent pneumothorax.
If you have questions please ask me.