To be honest, usually when men make up their minds about a relationship it can be final. And you did mention that he was already “slipping away”. Could he have been bored with the relationship? Could things have gotten stale? Or was it another woman? These things are important to consider.
One of the best ways to get someone back is actually by enjoying your life and bettering yourself. That same insecurity and jealous might have driven him away, slowly. Work on becoming more secure with yourself as a woman, completely. Men cannot help but be drawn to a woman who is full of life, grace, self-love, and passion.
I hope that helps a bit.
