Bad rib/chest pain and breathing problems?

I am 27 weeks now, with my first child. And I've had a lot of discomfort. I feel like I have asthma all the time. I have to stretch my arms above my head just to catch my breath. Along with that I have pain in my chest and very sore ribs. Working only makes it feel worse. By the time I get home after work each day I feel as if my chest is going to cave. Before I was pregnant, I weighed 117 lbs and only 5' with a very tiny build. I don't know if my size has anything to do with it, but is this normal? Any remedies? And do you think it is safe for me to work? I am on my feet all day and bending over constantly on hard floors. I need the money, but I don't want to cause harm to my little one.