Suggest Treatment For Low Grade Fever

I went to my personal physician two days ago, after a continuous low-grade fever. It has now been 14 days with it. He did a urinalysis, took blood and a chest X-Ray. All things came out that there was nothing unusual. he told me to continue to monitor things, and he would contact me Monday. I can keep the fever down with ibuprofen and Tylenol, but without them, my temperature ranges from 1.5 to 3 degrees above normal. Can you give me some kind of idea what s going on? I m a 70 year old man, who very rarely ever gets sick.