I had 2 babies close together and struggled to start losing the weight too.
It is now working but i have to say that ds2 is 11months old now.
Think the weight only started coming off when he was about 8 months.
And that was after i'd had a stomach bug (not a recommended diet plan!).
I have really had to change my eating habits - i'm not a gym person, or a diet club joiner.
And what i've found works is questioning everything i'm about to eat.
Not sure if i can explain properly, i don't calorie count, but i think will this be 'wasted' calories. will i really enjoy these 2 biscuits or would i be happy with just 1?
Am i about to mindlessly eat this cake or will i really appreciate it? that kind of thing.
Some things are habits too that take some breaking.
i would have 2 biscuits with every cup of tea, and i was having more and more tea to keep me awake (as boys were waking me up lots), so was getting through the biscuits!
And at friends we would always bring cake for the afternoon, but once you've started saying no thanks (and bringing a satsuma or something), it gets easier.
and they stop offering them to you which makes it easier again.
And when people start telling you how much weight you are losing, and how good you are looking, it all feels so good that you try harder.
And i gradually changed some things:
sprite - diet coke
butter - low fat margarine
full fat milk - skimmed, etc.
Have lost nearly 2 stone since aug/sept
back in some, but not all, of my pre-pg1 clothes
Oh & i read somewhere that it is very hard to lose weight when you are sleep deprived & when you have weird/active hormones.
Both common in new mums, so don't beat yourself up if it's slow to start coming off.
(oh and i don't know your history, but if you have PND you must surely be extra gentle on yourself.)
Good luck!