Scroll down to the bottom of the Discuss page and click on "Show your posts". There will be a notice near the top of the page that says, "Found (# of posts here) posts".
If you scroll down from this page, you can see all of your posts, showing your most recent forum posts first.
You can also find the number of topics you have posted in. Next to the word "posts" in the phrase "Show your posts" mentioned above, there is another link that says "topics". If you click on it, there will be another notice that tells you how many topics you've posted in.
