Pain while pumping!

So my baby is in the NICU and we just started BF five days ago so I have been pumping for the rest of the time as he does not empty me when he eats. We supplement with a bottle that has my milk in it and add a supplement. Anyhow, when I pump I get this weird painful pulling sensation on my right shoulder blade. Anybody know what this could be ? I also woke up this morning and my boobs were burning and very sensitive and the right side is very hard. I also felt a little nausea but it went away. Help please !