I was wondering how long after infection would you see a decrease in white blood cells? I believe my exposure occured almost three years ago and i recently went to the emergency room for bad migraines where i had tons of blood taken. I was told my white blood cell count was high and that I was probably fighting an infection. Also, is it possible they would test for HIV or would they need my consent?

it would be hard to answer that question because hiv effects everyone differently.

you wouldn't be tested unless you gave your signed consent so no would be the answer to your second question.
last if you have any doubts about your status... go get tested!
you have all to gain and nothing to lose by doing it.
good luck

Probably 6-12 weeks antibodies would be detected . It depends on the individual , some have opportunistic infections earlier while some after 5 years ie when the Tcell population must have been destroyed then signs of infections are seen. Testing in better than leaving in doubts because you might die even before been tested .