Only so far back, but if you scroll to the top of a forum page, and click the down arrow (carot) to the right of your user name, a drop down menu lists:
My Recent Posts
That only lists a few pages of my posts......
If you choose My Profile from the list that drops down, it takes you to your profile page. The top of the profile has an Activities tab, but again it only shows a few pages of my posts.
BUT if you click the About tab on your profile page, and scroll down to the bottom of that page when it opens, there's a link to either:
Find all posts
or
Find all started Topics
Those 2 links take you to a much more comprehensive list of your posts and Topics. But it you need to go back to before the upgrade last spring, you may not be able to find all your posts. I think it only goes back 500. So for me that doesn't even take me back to before Thanksgiving 2014.
Most if not all started Topics should be in it's list though. Barring an upgrade error that prevents locating or retrieving them.
