Is a patent possible or not?

I have a product idea in which there is currently nothing like it out on the market. I`ve done research and found nothing that is being marketed as what I have in mind.  It`s something that would require a certain "formula" so to speak. The ingredients to this formula are currently things that are used in other products that would do similar things, but are not marketed for the specific use I have in mind.  I`m not sure if this would be considered an invention or what, as similar things exist, but not for the use I have intended. Basically for my product idea, if I were to start making it myself and selling it (to stores, online, or whatever) what can I do to protect myself and to make sure that any other company who might see the idea and think it was a good one, wouldn`t copy it and make their own version of it?  And because they could happen to be well known or something, they would sell more than I ever could on my own and then I see no profit....I worry about this mainly because no product exists like this specifically for the use I have in mind.  But there are products with similar ingredients that do the same things, just not marketed in the way I am thinking.  Which is why I don`t think I could get a patent for this.  Or maybe I`m wrong...  Please correct me if I am!  I`d love any advice anyone out there could give!! Thanks!