Regardless where they were posted (Writing workshops, the lounge, publishing, etc) and without seeing all the single posts you've created as well. It gets a little tiresome having to search through all the categories of the forum to look for all of your threads if they're not all from the same place (writing workshop for example.)
I had a look around and managed to find a way! Go to the "Postings" tab on your profile. At the very bottom of the list you can find the options "Find all content by [user name]" and "Find all threads by [user name]".