I have been homosexually active (safer sex) for about 15 years but have never been tested for HIV. Recently I developed shingles on the face associated with painless swollen lymph nodes in the armpits. A CBC returned normal parameters. In these circumstances, would a standard CBC give at least some hint of lowered resistance due to HIV infection? Does a normal CBC measure T-cells and, particularly, CD4+ counts?

A CBC does not measure T cells, including T helper cells (CD4+ cells) -- you need a lymphocyte subsets blood test for that. Often, people with HIV will be somewhat anemic, with lower than normal total white blood cell and total lymphocyte counts. But I wouldn't count on the absence of these vague and non-specific findings for reassurance that you are HIV-. Bite the bullet and get tested -- it sounds to me like it's time you knew, one way or the other. Good luck!