I have long periods (6-10 weeks) of depressive episodes, followed by small periods (1-2 weeks) of hyperproductivity, lack of sleep, cheerfulness?

Agree w Dr. Seif. It is important to have this evaluated to determine if you have a mood disorder. Rule out unipolar or bipolar depression.
Mood disorder? We all get depressed but the cycle you describe might be a mood disorder. Please talk to your doc or a mental health professional. Help is available if needed. Peace and good health.