If the 500 mg doesn't help, up yourself to 1000 mg, and see if that does.
I don't know where you lived in the US, but it could be a change of climate (like if you moved from Minnesota or Maine to Columbia), a change in diet, stress, etc.
You might also want to make sure you don't have a secondary infection, like another STD, a urinary tract infection, etc., or something other than HIV that is affecting your immune system. Even a change in sleep can trigger herpes outbreaks.
If you shave your genital area, try stopping that for awhile, especially if you changed shaving products when you moved. If you want to groom, try a clipper or something.
I hope you find some relief soon!