This is such a good question. I really have trouble finding time. During my pregnancy I was an exercising dynamo. I really miss that.
I hear you on the low energy thing. I find that if I can force myself to exercise, I end up with more energy than when I started, so that's something.
Here's an idea- could you maybe learn to nurse your kiddo in a sling or baby carrier? I try to take an evening walk with DS when I get home at least twice a week. He rides in his Ergo and can nurse while we walk. It's very tricky to learn, but if your kiddo is old enough, it can be done. In cold weather, I just make sure he's wrapped up inside my coat so it's not too bad tto have my breast exposed. As the weather gets colder this might have to change. :\
Be gentle with yourself, though, mama. These early years, so much of what we wish and want to be doing falls by the wayside because of the HUGE investment we make in our kiddos. It will pay off. You are building a PERSON right now. What huge work! If you don't find time to work out and be a hardboy glamour machine with a perfect house while yo'ure at it, then you're like all the rest of us. :)
Good luck, mama.