Rewriting URLs within the webpage with a subdirectory - regex

Question

I've setup a reverse proxy and using mod_rewrite to rewrite the URLs. The issue I'm facing is that all the URLs in my webpage go to http://domainname.com/pagename
However, I want it to go to http://domainname.com/dir/pagename
I've tried a bunch of Rewrites but none seem to work.
<VirtualHost *:80>
# The ServerName directive sets the request scheme, hostname and port that
# the server uses to identify itself. This is used when creating
# redirection URLs. In the context of virtual hosts, the ServerName
# specifies what hostname must appear in the request's Host: header to
# match this virtual host. For the default virtual host (this file) this
# value is not decisive as it is used as a last resort host regardless.
# However, you must set it for any further virtual host explicitly.
#ServerName www.example.com
ServerAdmin webmaster#localhost
DocumentRoot /var/www/html
# Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
# error, crit, alert, emerg.
# It is also possible to configure the loglevel for particular
# modules, e.g.
#LogLevel info ssl:warn
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
# For most configuration files from conf-available/, which are
# enabled or disabled at a global level, it is possible to
# include a line for only one particular virtual host. For example the
# following line enables the CGI configuration for this host only
# after it has been globally disabled with "a2disconf".
#Include conf-available/serve-cgi-bin.conf
</VirtualHost>
<VirtualHost *:*>
ProxyPreserveHost On
# Servers to proxy the connection, or;
# List of application servers:
# Usage:
# ProxyPass / http://[IP Addr.]:[port]/
# ProxyPassReverse / http://[IP Addr.]:[port]/
# Example:
ProxyRequests Off
ProxyPass / http://0.0.0.0:8080/
ProxyPassReverse / http://0.0.0.0:8080/
</VirtualHost>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet
<Directory /var/www/>
AllowOverride All
Order allow,deny
allow from all
</Directory>
<Directory /var/www/html>
AllowOverride All
Order allow,deny
allow from all
</Directory>
<VirtualHost *:*>
# Proxy specific settings
ProxyRequests Off
<Proxy *>
AddDefaultCharset off
Order deny,allow
Allow from all
</Proxy>
ServerName do.domain.com
ProxyPassReverse blog.domain.com do.domain.com/blog/
RewriteEngine On
RewriteRule ^blog.(.*)$ do.cdomain.com/blog/$1 [P]
</VirtualHost>