I Have Itchy Red Rash On The Left Side Of Body. What Could Be The Reason?

HI have a red rash which started as what I thought was a bite under my left breast, a small part of the rash has also come back on the left side of my back - started 3-4 days ago and the spots now have little scabs - this is accompanied with a tingly/sensitive sensation mostly around my upper and middle left side of my back which has also moved to a section of my left arm and left palm - almost feels like my ribs are bruised. Any ideas? Went to GP yesterday and she said its possibly an allergic reaction to a bite but wasnt too sure...