Stop redirecting subdomain to main domain

Stop redirecting subdomain to main domain

How can I stop my subdomain from redirecting to my main domaine,
here's my code so that http://mydomaine.com always add the www
RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^www\.mysite\.com [NC]
RewriteRule (.*) http://www.mysite.com/$1 [R=301,L]
I've created a sub domaine (sub.mysite.com) that is in a sub sub folder of
my main site, and when I type sub.mysite.com it redirect to
www.mysite.com/sub/sub/
thamks for your help