Hello wildberry,
Just one thought comes to my mind, MRSA, it's an infection that is very hard to get rid of and has to be treated with complete protection from spreading to other people. A friend of mine had it and he went through three hospitalizations with IV antibiotics and they were like sores in his arm pit. Painful. I'm sure you may have already been tested for that but if not, it looks a lot like MRSA, (mersa)

Good luck,
dibug