You check your threads by going to My Rollitup. There you should see any threads you're subscribed to that have new posts, any threads YOU'VE created, the last threads you've posted in, and your recent rep points.
But that's only if you're subscribed to the threads. Go to My Rollitup, and click Edit Options. Under Messaging and Notification there is a Default Thread Subscription Mode. If it says Do Not Subscribe, then you're account is set up to NOT automatically subscribe you to threads you post in. You can either change that, or you can manually subscribe to each thread by using the Thread Tools at the top.
Did that help any?