What kind of virus causes pain in the right side when breathing?

also fever and chills? I have never had anything like this before. I am having extreme pain under my rib cage on my right side when trying to take a breath. Can't lay down because it is too painful. My son has had it and ped it to me. When my son first came down with it we even thought it was appendicitis at first because he was in so much pain. Obviously it is a virus since now I have it, but it causes EXTREME pain, what could this be? Also, I am pregnant and really worried, I already went to the doctor (and so did my son) and was told it was a virus, but thats all they could tell me.