The common notion is that Empaths act the way they do naturally. It just happens without their knowledge, just like the way the neuron system senses things around it. Some people believe that it is in their DNA.
The label of being an introvert and extrovert doesn't always fit certain types of personalities. It can be confusing to think which side you belong to as your traits don't always match one or the other. Your struggle to fit into the label probably means that you are an outgoing introvert.