very painful rash

hey i think i hve duckage i hve had this rash forever and nothing seems to help it except anti itch for short periods of time they checked for bed bugs but the cream burned and left scars on my skin i was wondering what it is tht i should do... and was also wonderin if i hve duckage is it contagious and what is the quickest way to get rid of it and how does 1 catch it... thanks sincerly Destiny