Thanks for your query and a clear picture.
Seen the picture and noted the history of a rash on the chest, abdomen and back.
This appears to be due to allergy to something.
You need to take an antihistamine and steroids under the guidance of your Doctor.
Also see why you are getting this, what is the causative factor, it may be in the bed-sheet, clothes or so. Clean them off and you will be fine.
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