htaccess not working properly

My current htaccess looks like this:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^(www\.)?site\.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/\.]+)/?$ index.php?page=$1
RewriteRule ^([^/\.]+)/([^/\.]+)?$ index.php?page=$1&subsectie=$2
RewriteRule ^([^/\.]+)/([^/\.]+)/([^/\.]+)?$ index.php?page=$1&subsectie=$2&subid=$3

I've edited the htaccess file. It should only use this htaccess for the main domain and not for subdomains, however subdomains still use this htaccess.

Anyone with more experience than me could point me out in the right direction? Thanks in advance.

Edit: Here is my current (and working) htaccess:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^(www\.)?domain\.com$ [NC]
RewriteRule ^([^/\.]+)/?$ index.php?page=$1
RewriteCond %{HTTP_HOST} ^(www\.)?domain\.com$ [NC]
RewriteRule ^([^/\.]+)/([^/\.]+)?$ in开发者_StackOverflowdex.php?page=$1&subsectie=$2
RewriteCond %{HTTP_HOST} ^(www\.)?domain\.com$ [NC]
RewriteRule ^([^/\.]+)/([^/\.]+)/([^/\.]+)?$ index.php?page=$1&subsectie=$2&subid=$3

Try this:

RewriteEngine On

# first, remove redirect to www by default if no subdomain
RewriteCond %{HTTP_HOST} ^domain.com [NC]
RewriteRule (.*) http://www.domain.com/$1 [R=301,L]

RewriteCond %{HTTP_HOST} ^www\.domain\.com [NC]
RewriteRule ^([^/\.]+)/?$ index.php?page=$1 [NC,L]
RewriteCond %{HTTP_HOST} ^www\.domain\.com [NC]
RewriteRule ^([^/\.]+)/([^/\.]+)/?$ index.php?page=$1&subsectie=$2 [NC,L]
RewriteCond %{HTTP_HOST} ^www\.domain\.com [NC]
RewriteRule ^([^/\.]+)/([^/\.]+)/([^/\.]+)/?$ index.php?page=$1&subsectie=$2&subid=$3 [NC,L]