I think your metabolism probably has slowed down, not because of the baby but because of starving yourself for so long...your body has probably become very very good at keeping hold of all the reserves it can 
I'm not sure of the best way to go about changing this but i think it will take time and common sense would say that more calories have to be the way forward, to start "reassuring" your body that there will be ongoing food IYSWIM? I would take the advice above, replace most of your carbs with protein and also up calories to 1500 a day.
Also try to focus less on weight - measure your bust, upper arms, waist, hips and thighs and if you can, get a body fat measurement done. Do more resistance training, aim to build muscle, which makes you look slimmer and more toned and increases your metabolism.
Replace sustained, steady cardio sessions with HIIT to blast fat and keep metabolism higher post workout. Long sessions of cardio can be counterproductive, especially if you are low on calories, you risk burning muscle instead of fat, which is NOT what you want. Make your workout 5 mins warm up, 30 mins weights, 20 mins HIIT, 10 mins core/stretching 3 times per week and check body fat and measurements once a month.