As others have pointed out, in the early days ("a month") of lithium medication it is important that your blood levels of it are checked frequently.

The therapeutic range of lithium is quite narrow - too little is of little benefit and too much can have undesirable side-effects. As a guide, the therapeutic blood lithium levels are in the range of 0.6 - 1.2 mmol/L.

I suggest that you get back to your prescribing doctor and ask him/her to check your blood lithium levels regularly - it may be necessary to adjust your dose up or down to make sure that your blood lithium level stays in the therapeutic range.