I feel you. I have no energy either. I wish I knew the answer. I do know I was doing better last year when I was walking a lot -- treadmill and outisde -- and I had a LOT more energy. When I fell off the bandwagon again, my energy level plummeted. I remember how hard it was with a toddler and work and how you feel like you can't possibly squeeze in time to excercise, but I do believe (even if I can't or don't always take my own advice) that getting in even 5 minutes of concentrated cardio would help you. Even just walking in place fast in front of the TV or doing jumping jacks, maybe your toddler could try some too. If not, they would probably get a kick out of watching mommy do them. I know, I know, I hear you saying, "but I'm too tired." Try it once, it's that first time that's the hardest. Each time will give you more energy to do it the next time! I might even hit the treadmill after that little speech . . .
Good luck. Positive thoughts.