Some viruses can take months to finally resolve. Since you are on immunomeds and steroids, have you contacted your doctor for further testing.
Could it be allergies? Could it be mono? What are your symptoms of the cold exactly?
Do you take your temp often and document it?
Do you have a sinus infection, throat infection or a chest infection?
Are you taking any otc meds such as pseudeopnedrine, expectorant, etc?
You definitely need to get things looked at by your GP...and for him/her to take you seriously considering this hasn't resolved as of yet.
Feel better soon,
q