Used items sold on Ebay

I sometimes sell used clothes, shoes, etc. on Ebay. A few weeks back Ebay informed me that my sales so far this year have exceeded $600. A 1099-K would be sent to me after the year ends. I use Ebay as a garage sale kind of thing to sell things at a loss. My only intent is to get rid of stuff that I don't need. Everything that I sell is at a loss.

I would like to know how I should be reporting this with TurboTax when it comes time to file taxes next year. Note that I don't have the original purchase receipts for most of the items that I sell.