I had this before, its an allergic reaction to a bug bite. I got bit once on my arm and it spread like wildfire with all these white looking bumps like that. Get some benedryl or like someone else said antiseptic cream and that will soothe the itch and slowly take it away
Looks like a bite from a small insect. Or an allergy to something.
I presume as the doctor could not identify these spots, he gave you no medication. If that is the case, apply an antiseptic cream, that you can purchase from the pharmacist.
They remind me of the bumps I got that turned out to be DH, which was related to my Celiac disease. You might want to get tested for that.