A Few Days Ago I Was Bitten By An Insect

A few days ago I was bitten by an insect on my upper arm. I had been around bushland. I do not know what insect. At first it was painful and appeared like a mere mosquito bite, but after a while it has spread to be larger than a 50 cent piece and has a red line has developed running towards my under arm. There is a clear bite mark. While it hadn't been Margery itchy or irritating, I have experienced moments of itchiness, a loss of appetite, fatigue and woke up this morning with numb toes. Although the redness is going down, the rash has spread beyond where it used to be after I traced around it and it went beyond the line. Do you have any ideas?