Please Help! What's wrong with me?

I have had on and off fevers, fatigue, chills, and swollen lymph nodes about the size of a golf ball (in neck, collar bone, underneath chin/jaw bone, and back of neck) now for about 3 weeks. Something is wrong with me, and doctors thought it was mono, but my blood work came back negative. They do not know what is wrong with me. Do any of you have any idea what I have?