Your model isn't domain model at all. It's a class diagram and that's probably confusing you.
A class diagram is like a modelling tool and can be used to model some subject from different points of view, on different abstraction levels.
A Domain model is more abstract and implementation independent model of the problem domain. Take a look at the example proposed in a previous answer from BugFree Solution. Domain model is typically used during the phase of analysis, to better understand and specify the problem domain.
Your diagram shows your system structure. It's a design artifact. It describes your system components in terms of 3 types of classes - boundary, controller and entity.
Further in your project you might make more concrete and detailed design models, like DB data model.
In practice, all these models are very useful and complementary. It is likely that your domain model will map well on the entity classes from your diagram.