Unable to prevent caching on .htaccess

I have a very annoying situation of where my website doesn't run updated code but instead just displays previous results. I have tried almost everything but it is still doing the same annoying thing. Here is how my .htaccess looks like

    RewriteEngine On
    RewriteCond %{HTTPS} !=on
    RewriteCond %{REQUEST_URI} !^/\.well-known/acme-challenge/[0-9a-zA-Z_-]+$
    RewriteCond %{REQUEST_URI} !^/\.well-known/cpanel-dcv/[0-9a-zA-Z_-]+$
    RewriteCond %{REQUEST_URI} !^/\.well-known/pki-validation/(?:\ Ballot169)?
    RewriteCond %{REQUEST_URI} !^/\.well-known/pki-validation/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
    RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
    AddType application/x-httpd-php .php .htm .html
    AddHandler x-httpd-php .php .htm .html
    Options -Indexes
    <IfModule mod_headers.c>
      Header always append X-Frame-Options SAMEORIGIN 

    </IfModule>
    #TRYING TO DISABLE CACHING
    <IfModule mod_headers.c>
        Header set Cache-Control "no-cache, no-store, must-revalidate"
        Header set Pragma "no-cache"
        Header set Expires 0
    </IfModule>