If you can't bring yourself for physical exercise try something simple like go out for a walk. If I can't walk I try to sit on my steps outside and read just to get some sun and fresh air and keep my mind occupied.

It can take some time for the antidepressant like your doc said, so be patient and try to use that hope to bring you through each day. If it turns out to be ineffective there are other medications to try. It takes patience but it works. In the meantime hang on and post here... We've had similar experiences and can offer good suggestions and support. Catnips volunteering idea is a really great idea.