If you look at any forum listing, topics to which you have posted are marked with a little "head and shoulders" icon.
If you open one of those, you will find at least one of your own posts.
If you then click on your name, you will get a profile summary. One of the items on that summary will be a link to "Show Posts" which will list all yours.
Before the forum was "improved", the link was also available directly as part of your profile icon at the top right of the window.