Losing my baby weight?

i put on 3 stone whilst pregnant (i was 8st and went upto 11st) i had my gorgeous girl 13weeks ago and im now 9st7lbs, but im now stuck there! i go out walkin with the pram as often as i can n im trying VERY hard to cut out eating rubbish but i was wondering if goin on a treadmill as short as 10mins everyday would make much of a diff or would it need to much longer?? i would love to be down to 9stone for xmas! (which i hope is being realistic!) but i would also like my jelly baby belly abit firmer!!! xxx