Depression saps your mental and physical energy. It's our natural response to fight against depression and pain, but that saps even more energy. It is my opinion that if you accept your illness just as a part of who you are and stop putting all of your energy into fighting, you may find your creativity returning. Keep treating your illness and definitely strive to recover, but if you can free up some mental energy you might start to become who you want to be. This won't be done over night and you will still struggle but it is something to work towards.

Remember that some of the most creative and successful artists throughout history have dealt with mental illness. That in and of itself should encourage you. And I believe it can add a depth to your art that might not have existed otherwise.