Nola,
Not long ago, I was dealing with pretty much the same thing. It didn't matter if I was taking a deep breath, breathing or just plain stretching. Now, it seemed to hurt worse if I was taking a deep breath or yawning. After a trip to my wonderful doc, he sent me home on Indocin and told me that I had Pleurisy.
Pleurisy is an inflammation of the pleura, the lining of the cavity surrounding the lungs. It is normally quite painful. It can be infectious to non-infectious. Regardless, you need to see a doc and let him know what is going on. A couple of xrays and a good listen to the lungs and the doc should have a good handle on it. If it turns out to be Pleurisy and you take your entire script of meds, do not be alarmed if you still have the same pain. It can take several prescriptions to get thru it. It took me three months to get over mine and then my doc had me take an extra two weeks for good measure. Now, I'm better than new.
Like I said it may or may not be Pleurisy so get to your doc and get things checked out. Always best to have a professional look at it and checks things out. I just play one on tv. haha
Nancy