You need to give us more information. What kind of product is it: consumer or business-to-business (enterprise)? Chances are, if your retention is nearly perfect and you've converted nearly all cold leads into customers, you're not charging customers enough money. Second, throwing money at ads -- when you have hardly any money -- is a typical mistake. Always try to earn attention before paying for it. Send some emails to bloggers about your pleased customers, ask your customers if they'll mention your product in their networks, write about your customers' success on your site (in your blog, etc.). When people don't want to freely talk about you anymore, then throw some money at ads to boost the old conversations.