In order to receive notifications of changes to messages you have posted, as well as topics you have subscribed too you need to make sure that you have enabled these notifications.
You can turn these on (or off) in your Profile, then under Modify Profile, Notifications and E-mail. There you see a list of topics you're subscribed to (and you can easily delete old ones). However, make sure that the setting:
For topics and boards I've requested notification on, notify me of:
is set to something else than Nothing at all, otherwise you won't receive anything. That also applies to Moderators... who will not receive moderator reports and so on.
Finally you have 4 options to select at the top of the page to turn automatic notifications on automatically, e.g. for all topics you post or reply to. That way you'll never miss a response to a subject you are interested in again!
Peter