I am having on again/off again pains on my upper left side. It is more around the rib cage area beneath my left pecs. The pain seems to grab when I exhale. Does this sound like something muscular? Should I just go to the emergency room or wait on a doctor's appointment?

I'd wait for the doctor, where you will get better attention anyway.
It does sound muscular, as opposed to heart or even heartburn. The high spot of the stomach is right under the heart, hence the term. Sometimes you can feel for the sore muscle. If you do find it, just soak in a tub or long shower or use a heating pad.