I think, I should get a shoulder stabilizer. I injured my shoulder when I was in school, playing softball. Since that, too much stress of that shoulder will give me sharp pain. The pain came back again when I started sewing. I have stopped sewing for a few months and the pain went away. Unfortunately, it came to visit again a few days ago. My not so newborn; 3mo already is getting heavier and wants to be nursed longer. That causes stress on my shoulder and I started to feel the pain. 
Stumble it!
