If you are using some version of Lightroom 6 or Lightroom CC (what version number are you using anyway?), try turning off the Graphics Processor (go to Preferences, click on the Performance tab and then uncheck the box)
If that doesn't work, here are two other things you might want to try
- Delete your preference file Preference file and other file locations | Lightroom 5
- Calibrate your monitor
- Turn off Auto Tone (as described in reply #8 here, uncheck the "Apply Auto Tone Adjustments" box)