I sometimes tend to overshop also when I'm depressed (probably, like you mention, because of the serotonin kick), but how you describe it makes it sound a lot like mania. Particularly the insomnia.

For years I took half doses of Nyquil or Tylonol PM to help me keep a regular sleep schedule. But even then, in the midst of an intense episode they rarely helped. They just made me... I don't know... tired but not very sleepy... if that makes sense. You'll need to see a pdoc to get something that would help with severe insomnia. (But by the way, if you DO happen to find an over the counter sleeping pill that helps, let me know!)

As Coco suggested, giving your cards to someone else for the time being would be a good move. Also, remember to go into your online store accounts and delete all the info while you're still in a good frame of mind to do so.