10-15 min workouts

Are these quick work outs really effective?  I try and do a 2 mile fast paced walk with my babies in the stroller every morning that is it nice or when we don't have alot of errands... otherwise I do my treadmill for about 16-17 min... sometimes longer then I incorporate a few minutes of weights.  Other days such as this morn I do my 10 min. Ab work out by Denise Austin then I do my weights in addition.  On top of these workouts I am doing slimfast for breakfast, fruit or yogurt for snack later, Special K or a salad for lunch or even sometimes a Fiber One bar, then will snack on a veggie or fruit later... then dinner.  Small portions and no seconds unless it's a veggie.  I also don't snack at night unless it's a handful or so of Special K if I get terribly hungry (around that time of the month) I am losing about 1-2 lbs each week of my recent baby weight (#4 baby born May 15th) I know I am not drinking enough water but I am drinking the sugar free Ocean Spray Ruby Red drink with only 5 calories.  Please ladies... tell me I'm doing something effective more than I realize.