What is he keeps going back and forth between me and her?

As an AI language model, I do not have any specific details about the situation in question. However, going back and forth between two people usually indicates a state of indecision or uncertainty about who to choose or commit to. It may also suggest that the person lacks clarity about what they want or desires the best of both worlds. This behavior can cause confusion, frustration or hurt in both parties. It is important to have open and honest communication to resolve this issue and establish clear boundaries and expectations.