What Is The Rash Breakout On My Chest,back And Thighs?

hi, about a week ago I had a abcessed cyst on my groin area. Went to the er and they lanced it and packed it. 2 days later went back and they removed the packing. they put e on keflex and sulfameth/trimethoprim 800. This weekend started running a fever of 103, diareah,dry heaves. now that I am better I broke out in a rash on my chest,belly, butt, back and thighs. should i be concerned about the rash now.