Suggest Treatment For Ribs Pain During Pregnancy

I have been having severe rib pain the last few days, especially when I lay down it hurts to even breathe, thus extrememly affecting my sleep the last few nights and being tired sure doesn't help the pain, I have an apt with my doctor in two days but called to see if there were any cancellations to get in sooner and the nurse told me I should go to the ER, is this necessary or will it be okay to wait until my apt? I am about 28weeks pregnant.