Is it possible some of those purchases were made using a different eBay account?
Can you see feedback for those purchases in your feedback received or left for others?
Can you search your Purchase History by item title keyword and find the transaction that way? In some situations the history by year may not show every transaction.
If you are certain you made those purchases using this account but you are unable to see them in your Purchase History, you can request a report from eBay of your purchases by date range here:
https://www.sarweb.ebay.co.uk/sar
Reports take a week to generate, then you must use the link within another week or the link expires.
