Hi Helen: Since depression has a biological component it could appear at a time when your biochemistry is depleted (by treatment, other medicines, alcohol or by your body's response to treatment). There are plenty of new antidepressants that have come on the market since Prozac became popular. Some target depression, some anxiety, etc. You may want to talk to your doctor about trying one of the newer ones. Even though things are going well for you (Hurrah!) you body could be experiencing chemical imbalances. Depression is not just emotional, but it is also a biochemical condition. Prozac deals well with certain types of depression, but other medications deal with other types of chemical imbalances (serotonin vs. dopamine, etc). Get thee to a doctor & talk to her about your options! Good luck! - Candace