Adding www. to url takes me to homepage

My two cents : could you please share with us the contents of your .htaccess file ?

This is beyond my own knowledge, htaccess syntax, but I believe there are strong chances you’ll be asked that question anyway.

RewriteEngine on

# Use PHP5.4 Single php.ini as default
AddHandler application/x-httpd-php54s .php

Options -Indexes

## RewriteEngine enabled

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule  ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
</IfModule>

# END WordPress

Check you DNS setting and see if the www subdomain redirects you.
Edit:
Post your DNS setting so I can see what they are set to… Unless you host it your self then don’t because that would be a security issue.

In DNS settings on my server, under CNAME, it says host record “www” points to “realtyparadigm.com”. Is that what you mean?

Make sure that it points to “@”. That is the correct setting. What it is currently set up as is a redirect. Which is most likely why it is causing your issues.

Well, everything worked fine before I updated to WP 3.9, so I don’t really want to mess with changing anything, except for what’s wrong with 3.9. Plus, I’m running wp multisite, and remembered following careful, precise instructions setting up all the DNS settings, so I’d rather not mess with them.

My host suggested adding this to my .htaccess file:

RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]

That seems to have worked. But is this the proper way to do it? I didn’t change anything other than updated to 3.9, and I’ve never had this problem before. I’d like to fix it for real, and I feel like I’ve just put a bandaid on it.