I think this is a common thing. With both my kids, when they were approaching two, I looked in the mirror and said wow! I think the hope is (as it was with me) that just chasing this active little person all day will help you lose weight, in my case I brestfed both my girls till they were 2 and I thought that would help also (it didn't). I was carring around some extra weight before the pregnancies, but I wasn't too overweight and I found I really needed to go on a "program" of diet and exercise to lose the pounds.
With my first child I started back to the gym at least 3 times a week, I know it isn't always possable to afford a gym and with your first it is hard to "give"them to the gym daycare. The gym was easier with my second LOL! I also signed up online to Weight watchers and over a period of months I lost about 40 pounds.
With my 2nd I decided after doing WW again for a month that it wasn't working as well (I had crept back up a little after I stopped the diet the first time around)I found I would "cheat" alot with WW and make bad choices food wise and my doctor suggested South Beach Diet. I read the book and liked that it was a plan that you stuck with after you lost the weight, I have a tendency to slip and have a terrible sweet tooth so I felt it sounded good.
I have lost 20 pounds and am 5 away from my goal. I am also eating better overall, more fruits and veggies. Even though I have had the stress of swithing around my schedule to go back to school nights I am still (overall) eating well.....the adjustment HAS made me reach for some comfort food and I have gained a little back this week but I feel cofident I can lose it quickly :)
Hope this helps you, and don't let anyone tell you it's easy!