My white blood count is a little low, and I'm so scared right now. Am I making too much of it?

I’ve always had a slightly low white blood count, but for some reason, I’m extremely worried this time. I suffer all of the usual anxiety symptoms, like fast heart rate, muscle spasms, fatigue etc. My doctor said that all my other tests in my lab work were stone cold normal, and he’s not completely worried. Do you think my doctor would have already discovered If I have a serious type of cancer?