Precise current measurement upto .05uA
The input noise of a OP7 is about 11nV/√Hz. The bandwidth (unless your circuit reduces it) is about 1MHz, so the expected input noise is about 10uV. With a gain of 8 the output noise is about 80-90uV.

You need to reduce the bandwidth.  Work out how often you actually need a measurement, and add low-pass filtering with a roll-off at about double the measurement rate.

Depending on your exact requirements, you might find a transimpedance amplifier a better fit than a series resistor &amp; voltage amplifier.