It is not really about combinations being used up, but more that combinations keep coming back again and again, because they seem to be so popular with the general public. I had to google that song "A Thousand Years", it is that one from Christina Perri? I am amazed that it has half a billion views (especially after listening to it lol), but yeah it doesn't matter what I think, as long as you feel that you connect with it. From a musical point of view, it is quite a simple song to analyze / reconstruct. However, if you do not know any musical theory or play an instrument, its going to be near impossible for me to explain it to you (especially if you wish to compose music).
What I recommend is to try and learn some basic music theory, then find the music sheets of that song you like, copy it and try to play it on an instrument, then try to analyze the song (find out what key/scale it is in, the tempo and time signature, what the chord progression is, the main phrases and where it repeats). Once you know that, then it is very easy to create your own piece (with your own key/scale, tempo, timings, chord progression, etc). As you see, this will take you some time to learn, but if that passion is there, you will learn.