I just ordered a bunch of items from my own store, and they're showing up in my sales reports as purchased through an affiliate. Help explain this please!

You were surfing around sometime in the last 30 days and picked up an affiliate cookie.

If you login using your regular account ID when you order being an affiliate sale should make no difference to you. You can't get volume bonus on your own purchases, and you get base price so there is nothing to deduct from your income.