Sorry for the delay in replying.
I am not sure how therapy would help me. I have never had a traumatic life experience (except the purperal psychosis) so there is nothing to deal with.
I didn't think extreme and rapid mood swings a symptom of depression; but no matter what I say, it is depression I am treated for. What does the screen for bi-polar involve.
You can see any mental health professional from Master's level or above for an evaluation. They would ask you about your symptoms in detail, paying attention to screen you for the symptoms of Bipolar and depression. A family history is also requested (Bipolar can be hereditary as can depression). From there a diagnosis can be made. The therapist would then let you know the courses of treatment that are recommended from medication to therapy. Self help is also an option to supplement any treatment.