Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain sudden development of a dull rash along with prickly touch and itching and development of 
cold chills and burning up seems to be most probably due to a sudden bout of 
allergic reaction that can be due to any 
bug bite or any contact with surface allergen..
As you have not eaten or drank anything nor washed or bathed, therefore the chances of other form of allergic reaction are less and either surface contact with any allergen or any bug bite is the cause for the reaction..
As the symptoms have now resolved it is a good sign but in case if it ever recurs in future, you should consult an Allergist and get evaluated and a thorough clinical evaluation and investigations like 
Patch test,  RAST test, Prick test etc can help in diagnosis and treatment can be done accordingly..
You can however take anti allergics like 
benadryl to relieve the symptoms...
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.