Suggest Treatment For Shoulder Blade Pain With Breathing Difficulty

I had a very sharp pain in between my shoulder blades that made it very hard to breath, It felt as though there were 5 people behind me with knives in my back, I'm very worried that it may come back, I'm normally a tough girl but this made me want to cry as well as scared me quite a bit. I'm 27 weeks pregnant and this is my second pregnancy, My 1st was delivered by c-section and I did not really feel any pains, So this scared me a lot. The pain is still there a bit but my fear is that it comes back again really strong... What could this be???