In the upper right corner, right under where it says Welcome username in bold, there is a link to Private Messages. To find messages you've previously posted, right-hand side -> Find Your Posts or Forum Links (top navbar) -> Find Your Posts
another way to keep track of threads that you started or posted in is to go to that thread and click on 'thread tools' at the upper right-hand corner of the page and choose 'subscribe to this thread'. on the window that appears, select how you want to be notified about the thread and then click on 'subscribe' and the page will refresh and take you back to the thread. you can access subscribed threads from 'my settings' which is located at the upper left-hand corner of the page. once that page loads, the newest subscribed threads will appear - with a button to 'show all'.
