invisigirl you can tweak your privacy settings so when you are online no one knows when you are online. Also I believe you can 'group' those on your friends lists into catagories... so for example you can have a 'family group' and anything you post to your other friends your family doesn't see etc.... You can also set your account so people can't find you on FB.

and as a last resort you can delete your account.

Hope you find some peace of mind soon with FB. - The social realm online can be aggravating at times