Sounds like you need to modify your exercise, diet and life style to get you where you want to be.  It's tough being a mother to a new-born baby (congratulations) and having the energy and desire to get into shape.  

It's all about maintainability - start by tracking what you eat, how much sleep you get and keep a journal of how your baby/toddler is impacting your daily routine.  Incorporate simple exercises that include your baby and some that you can do while the baby is napping (I'm assuming going to the gym by yourself is out of the question at this time).  

I'm a big fan of [FitDeck][1] - basically playing cards with various exercises on it that you can use to help guide/motivate you - for example, you can purchase the postnatal deck and pick out 10-20 cards to complete by end of day.

Some simple steps to take:

 - imagine/picture where you want to be - health wise - and write it down and hang it up
 - take pictures along the way so you can see the change
 - start slowly incorporating exercises into your schedule - don't burn yourself out
 - include trips to the playground, park, etc. with your baby as part of your workout, it all counts
 - track what you eat and start adjusting your diet
 - log your workout, join an on-line health/exercise community like dailyburn or LiveStrong to discuss with others

Good luck

  [1]: http://fitdeck.com/