First, it's good to review what type of notifications you are receiving. People with control panel access in your nation have default notification settings which can be changed by clicking edit next to their name and going to the Notifications tab. You can review and revise the notifications for everyone with control panel access to your nation by going to People --> Point People. From this list you can click edit next to each name and adjust the notfication settings.

When you connect a Twitter account to a broadcaster, the people following that Twitter account will be pulled into your nation. If you are the point person for new people, you'll get an email notifying you of this. This is probably what happened in your nation.

If a single person signs in with a different email address or Twitter handle, a new user record will be created for him/her. This can create confusion, especially when it is your own name / email address / Twitter account that is being pulled into your nation. You can merge these duplicate records. First, choose a primary record and copy the NationBuilder ID number from that record. Next, click edit next to the secondary record and in the lower right hand column where it says "Is this a duplicate? The ID number of the person to merge into." place the primary NationBuilder ID number into that text field. Click the green "Save person" button and the records will be merged. Note that a single user record can hold up to four email addresses with one designated as the primary address. Each user record can be associated with one Twitter ID.

Try searching for your name, email addresses and Twitter handles in your nation. In your nation, you'll find three user records. You can merge these records as described above.