How can I be sure I'm getting the right medical tests?

In February 2009 I became dizzy and faint and I ate several bags of candy to calm the shakes. I was tested for diabetes since most of my family has it. However, they said I didn't have it but gave me a testing kit. They also told me my white cells were low. I have gotten sick several times since then. However, the dizzy spell had not come back until this Sunday. It felt like someone turned the lights out for a second and it took me approx 15 to 30 min to get back half-alert. When I went to the hospital they did a brain scan with no results however my x-ray showed something and very low white count where the hospital asked me if there was a chance of AIDS. I have been tested for AIDS many times with negative results, however I have been weak and light-headed lately. My question is, what questions should I be asking to get the right test done? Something is wrong but I'm not sure if I'm saying enough to get the right test and should I be worried about the white cells?