Most genital itching in women is not due to any STD. Everybody's genitals itch from time to time, but prominent itching with redness suggests a yeast infection, which almost every woman gets from time to time. My guess is that the increased tenderness and swelling are simply because aggressive itching broke the skin and might have led to a minor bacterial infection--exactly as you suspect yourself. No STD is likely to be the cause. You should see a health care provider and not try to figure this out on your own or by online forums, this or any other.
Good luck-- HHH, MD
Also, even if I did have HIV (i tested negative out to 4 months) does this sound like a later symptom caused by it?