It sounds to me like you are probably not breastfeeding because I dropped the pounds so fast due to breastfeeding my baby, I can't give any advice for this child, but for the next to loos the weight fast don't use formula, breatfeeding takes a lot of calories from you and you'll shed that baby fast so fast you won't believe the scale.
I guess since it's too late now for that though, for me what has worked in general for loosing weight is cycling at the gym (or buying one for the house like I did) It's a really easy exercise you can do for a long time because you are sitting, but you can burn a lot of fat in an hour. And if you like to read the time goes by fast, or if you don't like to read you can bring it out into the livingroom and watch your favorite show or two while cycling. And regularity is key, I used to cycle 6 days a week and do power style yoga for an hour once a week (this really makes you sweat too and is great for muscle tone and flexability)