Someone once said that there are no new stories.
He was right.
All stories can be categorized into one of many motiffs, all of which have been done for as long as stories have been told.
So how do you make your story original?
You don't. But you DO make it interesting.
First, let me slay a myth--people don't read your story to find out what happens at the end. The underlying story structure that we, as humans, have lived with for thousands of years says that good wins, problems are solved, characters learn lessons, and life goes on.
Even in a murder mystery we know the killer will be caught in the end. And in a well-written murder mystery we even have a richly satisfying "I KNEW IT!" moment when the killer is revealed. You see? We already knew.
So what makes us read a story? The middle. The stuff that gets us to the end.
We want to see what happens to get your characters there. We want to see their struggles, their desires, their pain, their courage, their cowardice, their triumphs, strengths, weaknesses, warts and all. We want characters to be REAL to us. We want to feel for them. We want to feel WITH them.
Your characters don't need to have green hair or seven toes to be interesting. They don't even need to be described in great detail. They only need to do things that your readers can relate to, can understand, can empathize with.
Another aspect of making a story more original, or interesting, is to avoid cliche. Avoid the first thing that comes to the collective human conscience. For example, if a kid is walking across a playground and comes across a hoppy-taw, what's the first thing he might do with it? Sticks it in his pocket? Maybe. Play a game of hopscotch? Possibly. Those are pretty common answers. What's slightly more interesting than that? Maybe he goes on a quest to discover the owner of the hoppy-taw. Maybe that gets him into some other kind of adventure. Maybe he knows whose it is and decides to keep it. Maybe there's some tension between him and this other child. What could it be? How might it be resolved?
Keep thinking. The third or fourth idea will likely be considerably more original. And that idea will lead to others, and the process begins again.
So, originality is less in the story structure and more in the story details. Give yourself a break. Let yourself use the standard story structure and enrich your stories with the treasures you can stuff inside it.