It sounds like you are doing heaps of exercise, walking with the pram is great resistance and burns a lot of calories. I did the gym etc for the first 6 months and nothing happened and then around 6 or 7 months after my DD was born it just started to fall off through walking and breastfeedng. The only suggestion I have is try to hold your tummy in while you walk, it strengthens the core. But you are doing everything right, it won't happen over night but it will happen x