Hi
There are three things that you can do..
First:At the very top of every page there are two links, next to your avatar..
Show unread posts since last visit.
Show new replies to your posts.If you click on
Show new replies to your posts. you should see a list of messages you have responded to.
Second:All threads you have posted on will have this symbol next to them on the left hand side of the index

- see the little face, that means you posted on that thread..
Third:When you post on a message there is a link below the text entry box called
Additional Options... if you click on this link you will see a check box that says
Notify me of replies, if you tick this box then look in your
Profile under
Notifications and Email you will see all the topics you have selected to be notified on.
You can also edit your profile so that
Turn notification on when you post or reply to a topic is on by default.
Thanks
TSD