What is wrong with me?

I had what the doctors described as "an infected follicle that's ulcerated and is now healing beautifully" on my forearm. I now have another one on my leg, and possibly two others forming of my other arm. What is causing this, and what is it called? I also have a cyst-type thing under my arm (it's pretty small) which may or may not be the same kind of thing that was on my arm.