I had a neg lyme test, was treated for a month with abx., had herx at that time. now a yr later low grade fever and joint pain. could this be lyme?

Unlikely: Define herx. If you had Lyme disease and we would to know the findings at that time and If you had appropriate antibiotics you should be fine BUT if you were reinfected then you could have Lyme disease. Your physician will be able to test lab test to help clarify. There may be many other diagnoses so you need an evaluation.

Could be others: Depending on your exposure to ticks in your neck of the woods, you should have also been tested for other tick-borne illnesses since they travel in packs (Anaplasma, Babesia, Human granulocytic/monocytic Erlichiosis, others). If not tested, you could have one of these other infections, including Lyme, or else it my be entirely different diagnosis. It's best to get it evaluated by a doctor.