Where to check what apps I have purchased
I think what you want is the My Orders page.

This is reachable from the Play Store web site under the "gear" menu in the upper right.

I see all of the things I've purchased from Google Play, including apps, music, etc.



For what it's worth, there does not appear to be a way to get a list of your orders from within the Play Store app. However, I do see a list of transactions in my Google Wallet app, although admittedly they're not all necessarily from the Play Store.