This could be a possibility, but it is hard for me to say without more information and I recommend that you continue to work with your doctor
and explain your concerns. In general, lymph nodes that are this size are not always normal, which would possibly explain why your doctor has ordered these tests. As you suggest, it could be due to some infection that your body is fighting or has fought in the recent past. You are correct in recognizing that many times the white blood cell count or other changes will be manifest in the blood tests that were obtained, and those being normal could be indicative that there is no active infection. This is not always the case, however, and so you should speak with your doctor. There are obviously many other reasons that you could have the swollen nodes, and there are some additional findings that may have arisen from the ultrasound
that could tell your doctor more information. Some of these include the shape of the nodes, among other things. Depending on your doctor's level of concern, he or she may indicate that you undergo some sort of test to sample the node, or more testing to determine what is causing the swelling. Please continue to work with your doctor, and discuss this question with him or her.