The switched capacitor voltage booster of the type you built is not very good at being a regulator. The output voltage will droop with the amount of load put on the outputs. The negative output will droop more than the positive output because the already drooped V+ output is the supply for the inversion to V-.

With your existing circuit you could look at the following suggestions.
1) Try the 7660 with larger capacitors.

2) Find an opamp that has much lower supply current requirement. Linear Tech and TI both have parts that have supply currents in the less than 0.5 mA range.

3) Work carefully to design the opamp circuit with higher resistor values. Modern precision opamps in a circuit with a good PC board design can often be made to work very well with resistors in the 100K range instead of the 1K range.

4) Look for an opamp that has a supply voltage rejection that is very high. Then scale your operating point to a lower voltage range using resistors so the opamp does not need to work at full +/- 9V.

5) Look at rail-to-rail type opamps. These often let you do analog circuits in the single supply 5V realm instead of the older dual supply scheme.

6) You could trash the 7660 completely and find a power supply chip from National or Maxim that is a switched capacitor low power device that can regulate its output. Some of these chips dynamically adjust their switching behavior to achieve a constant output. Something that the 7660 cannot do.

Michael Karas