The window period for HIV can range upto 6 months. Since, your last antibody test was after 6 months and still negative, it is very less likely that you may be infected.
Do you have any swellings, weight loss, fever?
CBC is not a very good test for HIV. The various parameters may rise or fall depending upon situation.
A CD4+ T cell is a good marker of cell mediated immunity
In most cases, 3 negative antibody test indicates negative HIV. What did your doctor say? Can you explain about your leg pain?