Negative Ohm reading from a Electrochemical reaction?
How could I use the negative Ohms reading? 


You're using the meter the wrong way. A meter is set up to have a particular low voltage and measures how much current flows. Since your electrochemical cell has a voltage and creates its own current the meter reading goes whacko.  


  Should I be collecting data in a different way? 


If measure current that would give you some idea. In a better controlled analytical chemistry experiment a special electrode pair with two flat plates is used so that the geometric configuration stays exactly the same.