Read Thread: My Recent Posts
There already is. Top left corner, it says First or Previous. You can go backwards one at a time or go all the way back to your first post.
I don't use that widget. I go to my Profile page and click on recent posts. Then the buttons are there. You can do that from any profile page.
OK, it took me a while to find the Recent Posts button because it's such a cute work of art. Yeah, I can see how that would work -- but I still think it'd be handy to have a "My Previous Posts" button at the bottom of the widget. Or perhaps just a button that'd take you to the same place the button on the My Profile page takes you.
'Tis been done!