well, you can click on your user name. That page will show your last post. Then, you can click the 'Search for all posts by this user' link on the upper left to search for previous posts (I'm not sure, this function may be available to community supporters only)
Alternatively, you can go to any forum and click 'thread starter' to order the posts by the userid of the thread starter, instead of most recent first.
As it is part of the search feature, it should only be available to Community Supporters.
You can, however, click on the User CP button on top of the screen and then go to the Subscribed Threads page. Unless you did not subscribe to the threads, you should find all threads you started or reply to in there.
One method that works (but may take a little time): click on Thread Starter (the title of the column just above the name of who started each thread). All threads in the forum will no be displayed by alphabetical order of its starter. Then edit the URL line of your browser, locate the "&perpage={number}" bit (if it ain't here, type it yourself) and replace the number by 200. It's the maximum. So, &perpage=200.
Then you may look at the previous pages to find all the threads you started.