I am exactly like you, a 24 year old new mommy, gave birth last august, gained weight up to 204.6 lbs and when I gave birth I droped to 182.6 lbs, and now I started dieting (on the new year) and droped down to 169.4 lbs so far!!
I am a breastfeeding mother too, I dont know wether you are or not?? so I'm trying to eat as healthy as I can, maintain a good caloric intake, exercise on the elliptical machine, and still drop weight.
I read a good book called "burn the fat, feed the muscle" for bodybuilder tom venuto, where he exposes all the secrets to a succesfull balanced diet, that works by boosting your metabolism and preventing your body from going into starvation mode.
I My goal is to drop to 128 lbs til summer time (may-june), so when I started dieting I ate a total of 2,000-2,200 cal/day, and did cardio on the crosstrainer 30 min. and that's when I lost the intial 10-12 pounds,but then I dropped my caloric intake to 1,500cal/day and I noticed that my scale got stuck at the 169 lbs!!! I believe my body went into starvation mode as you said. as my maintenance level was on 2,600 cal, breastfeeding takes at least 300 cal, and cardio 400 cal, I'm going to try to stick on 1,800 cal/day and see how it works.
my worst nightmare is when I get on the scale and see the weight is still the same!! or even increased!!!
Also, I read in the book, that you should increase the exercise intensity and duration gradually, to prevent your body from undergoing into adaptation mode. then instead of needing an hour on your machine to lose the weight, you will need more than an hour to lose the same amount you lost in the begging, maybe you should take it easy on the training as well. start off with 30 min, moderate intensity, or try the HIIT (high intensity interval technique) did you hear about? it claims to keep your metabolism up several hours after workout and takes only (20-30 min)..keep me posted with your updates, hopefully we can help each other lose the pregnancy weight and become even better than before