Like he said, there is nothing more important than trust. With trust a relationship can survive almost anything. Without it, it can't survive at all. Cheating is a total betrayal of trust. The relationship can be saved, but only if the party that cheated is committed to rebuilding that trust, and the offended party is willing to let them try. It doesn't sound like your ex-partner is willing to make that kind of commitment.
*MySmiley*
"Bustin' makes me feel good!"
Ghostbusters, by Ray Parker Jr.