I Don't Know What Bit Me (already Had It Treated,

I don't know what bit me (already had it treated, but it stung real bad and then about 12 hrs later it was a dark red ring with a white spot in the center. It was on my stomach and the itchy burning rash that fanned out from the small mark was the size of a dinner plate by the time I saw the DR. They gave me Prednisone and Bactrim which seem to have gotten it under control. I just wanted to know WHAT bit me since I didn't see it, I just swatted it away when I felt the stinging/burning sensation on my stomach.