In your second post you say your moods switch from depression to semi-normal. That doesn't meet the criteria for bipolar disorder. Have you looked at atypical depression? It's different from major depression in that there is reactivity to events (ie you can feel better for a little while in response to an event or trigger).
I would imagine Lamictal would have a benefit on depression in general, since it has a reputation for being good with bipolar depression.
There's also cyclothymia:
Cyclothymia (Cyclothymic Disorder) Symptoms, Treatments, Causes, and More