Hi there DepressedMom and Welcome to Healingwell!
Have you been diagnosed with Post-Natal Depression, or is it a different 'kind' of depression? Have you tried talking therapy? I know this sounds warped but have you tried exercise as a method of inceasing your energy? I know it sounds backwards since exercise uses energy, but I know a lot of people who have tried this and have found that it works. Also, changing your diet may help your energy levels as well. Insteasd of fried chicken and chips (for example) how about a warm chicken salad? There are loads of recipies out there that are easy to prepare and make, requiring little energy, and are much better for you. You may also find that you lose some of the weight that you have put on.
I hope that this is of some help to you... Keep us posted!
Darren