i already have the ground connected.
Yes but how is the rest of it connected up.
If you want specific advice about a circuit you have to post the schematic of what you have made.
Arduino is reading weird things from the op amp
No the arduino is reading exactly the right thing, if it appears to you to be weird then it probably is not a good circuit you have made. This is either the design or the implementation, without a schematic I can't tell you which.