Like Lespaulsmith said, this girl has issues with herself. Always feeling lonely even when she was with him, but now they're not together and she's seeing someone else. The last part of the song explains that when they were together she didn't give her all, because of how's he was then. But now she's met someone else and she's changed and she does genuinely give her all to this new person and Ben feels this pain because he wishes that she was that way when they were together. She loves this new guy as if all before him made her feel lonely, but that's alright with Ben.
Like Lespaulsmith said, this girl has issues with herself. Always feeling lonely even when she was with him, but now they're not together and she's seeing someone else. The last part of the song explains that when they were together she didn't give her all, because of how's he was then. But now she's met someone else and she's changed and she does genuinely give her all to this new person and Ben feels this pain because he wishes that she was that way when they were together. She loves this new guy as if all before him made her feel lonely, but that's alright with Ben.