I'm in pain and the doctors can't seem to diagnose it.

I haven't been diagnosed with cancer but doctors keep leaning to it. I have had months of CT's and MRI'S and numorus blood tests done. Still nothing except for a 17000 white blood count and major pain in lower back due to SI joint that is deteriorating. I wake up at night with stabbing pain in my knees, night sweats and I feel tired all the time. Please, is there someone out there having same thing and feeling like the doctors in this day can't find an answer. Haven't worked in four months due to chronic pain and all the drugs every doctor puts me on..