When replying to a thread there is a "Subscribe to this Thread" check box under the "Reply to Thread" "Preview" "Attach Code" and "Cancel" buttons. Are the emails you are recieveing about thread subscriptions? If that is the case then every time somebody replies to a thread you are subscribed to you will recieve an email about it. I am guessing this is the problem.
I am sure there is a simple way to unsubscribe to everything, which would be a better way to fix this, but if you cannot figure out how to do that, and I do not know how to either, you could click on the "Customize" button (located under the Navigation bar), and find the option that says "I want my thread subscriptions to be delivered to my private message box instead of by E-mail." and check the bullet labeled "Yes" under this.
In this way all your thread subscriptions should flood your PM box instead of your email inbox. Hope that helps.