As a student, you can review a list of all your forum posts:

On the right-hand side of the screen, click on 1) your picture or initials and select 2) Profile. 

In your profile, you will have the following two links for viewing forum activity:

Forum posts: All discussions you have started and replies you have posted

Forum discussions: Discussions that you have started

 A list of your posts should look similar to this screenshot. Note, if you would like to save these posts, you can copy and paste them into a Google Doc.