For starters a binding doesn't make the person love you, a binding will keep having the two parties bump into each other. Bindings are usually undone by the caster unless you're lucky enough to find the item used in the binding and untie it.
It doesn't sound like she's cast anything. Relationships end, sad at it may be. You said it was a rocky one, and he's a cheater, so perhaps it was only a matter of time. You say he's acting different, love can make people act strange. If you want him back, try talking to a couples councillor, but if it ends, realize you can do better, deserve better, and will find better.