No! No worries here...  The *only* way that people can read your Protected Posts is if you add them to your Protected List, yourself (adding someone to your Subscriptions list is not the same as adding that person to your Protected List, and nobody is automatically added to your Protected List).

If you've added someone to your Subscriptions list, and you also want to add that person to your Protected List, you can check out the instructions here:

How do I add someone to my Protected List?
http://help.xanga.com/howdoiaddsomeonetopplist.htm