What Causes Boils On Stomach And Waistline?

I had a boil on my stomach for which the doctor prescribed an antibiotic called cephalexin about two days ago. I also noticed another boil around my left waist line and the doctor said it looks like a mosquito bite. Two days later this has grown and is red and swollen,so i thought of getting another check-up from a different doctor who said i should continue the antibiotic and also prescribed a cream called elocom. But the same evening i have started getting hot and cold flashes and a headache is just driving me nuts. What could the problem be???