What can I do if I'm doing more work than my coworker?

There are a number of things you can do if you think that you are carrying more of a load than your coworker:

1- talk to your manager and ask for a more balanced workload

2 - have a relaxed conversation with your coworker -- "I am feeling that our workloads are not the same - can we talk about this and  possibly make it more balanced?"

This can be a difficult conversation, but it can also be a productive conversation. Be sure not to blame, accuse or complain. Be a problem-solver!