If you really don't want the easy & goodlooking option of a opensource CMS (wordpress, cmsmadesimple, drupal) you could use sites like FreeCssTemplates.org to find a nice looking template and start working from there.
With only three weeks at hands your current lack of experience will clearly show, it takes a lot of practice to make a professional looking site from scratch. No offense intended here, of course.
But in the end, I would advice Wordpress + a free template.