Justin Bieber - Nothing Like Us Lyrics Meaning

I could tell that this song describes how he truly feels about Selena,and to be honest I feel his pain you know

-At first Justin says he is thinking about what he and Selena had in their relationship and he admits it's hard how it ended ,and he is wondering how can she just walk away without looking back like nothing has ever happened and he is wondering was she drinking to forget this pain,because obviously it wasn't easy for him at all and He wishes that he could have given her what she needed and he says that nothing can replace her at all no matter what nothing can make him feel the happiness and the joy he felt with her, and he says there is noone he can ever depend on and understand and he won't be lucky with the chance to find such a great love, and He says he gave her all he had to give but he is wondering why would she push him out of her life so coldly and he is lost and his doubts and wondering he says he is used to make her happy and cheerful and he says it's from the past they didn't last and everything got ruined and he is guessing it was meant to be and he is wondering was it worth the pain and the wondering? pointing out that they were perfect together ,ouch right?