They only do a western blot test if you have a positive on the elisa then they confirm it with the western blot
sometimes they will do an elisa 2 times before the wb
look your negative dont worry ok
The first test is done because it is really sensitive (though may pick up other vross reacting proteins)
The second test is done (if the fiest test ws reactive) because it is really specific (it won't pick up cross reacting proteins).