There is nothing new under the sun. There's no such thing as an 'original' plot idea, or it would never be used because it sucks.
However, how you ARRANGE and construct those plot ideas are original. That's where your stories come from.
Every idea JRR Tolkein had was stolen from another source, He simply added a new language to it, filed off the serial numbers, and created a new series.
You don't have to have original ideas to be an original writer. You simply have to be original as a writer... and there are as many original writing styles as there are writers.