To check all the posts you have made:
1. Login and click on your Username on the top right of the screen. That should bring a drop down menu with many links. Select 'Your Profile Page' from the drop down.
2. In your Profile page that opens up, select the tab 'Postings'. It will list all your recent activity including the posts you made, threads you created and media you uploaded.
3. To see the posts made by you, scroll down in the 'Postings' tab and you should be able to find a link that says 'Find all content by <<username>>'. Click on the link to see all your posts.