Could you also have something that could bring you down physically, in addition to the depression? Like low B12, low Vitamin D, low iron? I think depression alone can definitely be the cause of your sleeping and feeling so physically weak, but maybe you'll get lucky (I know, lucky, ha!) and find you have something else to treat that may help you.

I had a very low Vit. D level, and was so weak I could hardly be out of bed at all, and taking a shower took everything I had. I treated the low D and was surprised to find my energy and stamina improved significantly within about 8 weeks. Still depressed, but no longer feel like I'm gonna die just from taking a shower. It's a start.

Hope you find some relief soon.