I think you need to file a complaint with the hospital and perhaps get some kind of representation. I am not the sueing kind but they put you at risk with their negligence and you now have to go through the agony of getting tested and deal with the emotional and mental stress of this all. Perhaps if you talk with your advisor you can tell her about the contaminated needle situation along with your other health problems and they would be able to work with you.
Hope you feel better soon with the zoloft. I find that a small dose of antianxiety meds to help relax my bum so it hurts less. Valium is used as a muscle relaxant more than the others but I understand your reluctance to add too many meds to the mix.