I feel like i can't take a full deep breath...100% o2sat. no noticeable sob. no "pain" but a dull feeling in my sternum area. my family dr said muscle?

Can do a lung test: In such a case, a patient can do a pulmonary function test (spirometry). Many primary care doctor's have a machine in the office. Otherwise, the allergists have machines in their offices. The test shows how much air is breathed in and breathed out, and how many seconds that takes, plus whether or not there is any restriction to air flow.

Atypical chest pain: The work is based on the age and associated conditions and the risk level for the vascular disease. Having said that I am sure your family doctor considered all these and cam up with the conclusion for muscle pain. It is common to have costo chondritis in the chest rib area which may mimic a chestpain.