plateau. They suck. What it usually means is your body is in a rut and used to the activity you do so it being the efficient machine that it is - your body can minimize how many calories it expends to do the same activity. The other reason for plateau can be that even though you have lost _weight_ you've lost muscle from eating too little nutrition/calories and not exercising so you weigh less but are fatter or lost a combo of fat/muscle that still leaves you will more fat than muscle. It sounds way more like the first situation than the second, for you.
So you have to ramp it up a little and/or do different things. Once you're where you want to be (and make sure your mom's eyes aren't telling more truth than yours) then you can just maintain doing moderate activity but now we have to go harder for moderately-intense with some intense bursts thrown in for for a nice boost.
Here is a target heart rate counter to use as a guide. Checking your pulse while you workout is a great tool for knowing at what percent of your maximum heart rate you're working at. A super fit athlete might train at 90% of their maximum heart rate but we should stick with 60-80 percent, I usually shoot for 65-70 with short bursts of more intense exercise in my longer (45 minutes) moderately intense workout (mainly I jog in place/
do the Walk Away moves in front of the TV or do Walk Away the Pounds the 3 mile tape).
If you've been keeping track of your measurements that's a fantastic tool for judging what's happening to your body.
If you find it really hard to maintain at a lower weight you may want to accept your natural weight is at a slightly level higher than you want. If you're just in a plateau change it up and do different things and go a bit harder/longer (don't kill yourself, it won't help). Since you already are eating plenty of good foods made of veggies, lean proteins (for strong sexy muscles) and other non-veggie good carbs - make sure you didn't cut out the good
unsaturated fats, you need some of those to lube your body and brain, you got that part down.
And finally, sometimes a scale plateau does just mean your body is busy adding muscles while ditching fat.