New writers worry about the wrong things. Some of the most prominent worries are: someone stealing their work or their ideas, worrying about getting an agent, or writing a plot that's been used before.
There are a lot of things about writing that have the ability to create intense anxiety in an aspiring writer, but, of all the fears I didn't list and those above, writing a plot that's been used before is the most easily cured.
The cure is easy because, write this down and commit it to memory, there are no new plots. Stitch it into a sampler if you wish and hang it above your computer. Depending on which source you site, there are only 3-9 plots in all of the world's cultural history. Everything else is a variation of that finite number of plots.
The way you make each plot seem different, new, and exciting is all in the execution. It's what you bring to the plot in terms of your word choice, the way you tell a story, the spin you put on it. Of course, word choice, sentence construction, and the way you, not anyone else, write that story are all matters pertaining to your author's voice.
Quit worrying about not having an original plot, because you don't. What you need to be most concerned with is getting the story written. Execute the plot as only you can because there are no new ones, only new ways of telling the same kind of story that's been told for millennia.
Willa Cather once said: "There are only two or three human stories, and they go on repeating themselves as fiercely as if they had never happened before."
You're the spin doctor of your writing ideas. Put your own spin on an idea and just write. As Larry the Cable Guy says: "Gitterdone."