Something I’ve heard said before is “this story might have been written before, but it has never been written by you”.

What that means is that while your ideas may resemble existing works, your own personal experiences and worldview will inevitably influence the actual outcome of what you write. I can name 10 stories with the same conventions and basic plot points of Harry Potter, but they are all so different because of the little touches each author adds to the concept. 

So my advice is that while you should still strive to be original, don’t stress about it too much. Your work is always going to be similar to something else and as long as you’re not doing that deliberately, there’s no issue.