It is unlikely that drainage in the back of your
throatCancer - throat or larynx
Throat swab culture will cause headaches. However, it is possible that you have some sinus inflammation that is causing both the drainage and the headaches. The drainage is not always visible in the throat, even when it is a problem. This is most common when it is from an infection and is thick and discolored. I would suggest talking with your doctor about the sinuses as a possible cause of the symptoms you are experiencing.