Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.

it sounds to me like you had a panic attack, and that triggered a bout of depression, to protect you from the panic attack (its my own personal opinion that that happens... ive never read it anywhere, and i might be full of crap here)
after a while, the panic subsides enough for you to lift yourself out of the depression... but then it comes back
do you know what triggered your panic attack? its very helpful if you do know... then you can work on not getting panic'd, or triggered by that type of event anymore.