What Causes Headache, Sore Throat And Very Swollen Right Lymph Node?

I've had a headache, sore throat, and very swollen right lymph node. Today is the third day of this and now I can't talk nor swallow anything because the pain is that bad. Also I can feel my left side swelling up too and I have a very stiff neck. Are there any over the counter things I can take for this? What could it be?