I know I keep repeating myself, but it's not your job to convince some guy that you are the woman for him. It's also not your job to analyze every syllable he utters, his every facial expression, or the deep-seated cause of his compulsive knuckle cracking.
If he says he doesn't want a relationship, take him at his word. Keep moving until a braver man appears. If he wakes up one morning and finds he didn't mean it, he'll be sure to let you know.