why have i stopped losing weight?

Question
i'm 16, 5"6 and weight 140 pounds i have been on a diet for about 2 months now which consists of no chocolate, no fatty foods, nothing too high in fat and generally eating healthy!
a typical day i would eat; cereal (2 wheatabix) for breakfast, a cheese roll or salade options offered at the school cafeteria for lunch and try to maintain a low calorie dinner around 500 cal or less. i don't snack I only eat necessity fruits like bananas, apples, peaches, plums and grapes.
sometimes i find find it quite hard to stick to a salade for lunch as food at school tends to vary and its hard to know what will be on offer!

I do sport everyday. A typical week consists of; trampolining on monday nights for about 45-60 minutes, not to strenuous as there is alot of time spent waiting for other to get off the trampoline! On tuesday i do an hour of strenuous swimming and usually manage about 60-70 lengths, On wednesday i have a sports lesson in the morning lasting for one hour, but isn't taken too seriously (due to the fact that our class isn't taking it for GCSE) and about 45 minutes in the gym in the afternoon usually burning 300-400 calories, On thursdays i do swimming again and manage to do around 40=50 lenghts, Fridays i have another hours lesson of swimming but again as it is our sports lesson isn't taken as seriously as swimming on tues, thurs and saturdays also i have a trip to the gym in the evening and finally on saturdays i do another hours session on swimming and do about 40-50 lengths.

my problem is that i lost a stone quite quickly, but the past couple of weeks (about 3 weeks) i just don't seem to be losing anymore weight and i really can't understand why. i don't want to have to cut down any more food either, and i dont particually want to increase the amount of food i eat because i am worried about putting on anymore weight. So in desperate need of advice!

thank you

Answer
Harriet,
It sounds like you are doing everything right, and you are at a healthy weight.  What is the goal weight you want to get to?  I would recommned you eat less at dinner, move those extra calories to your lunch, your body will have more time to burn it off.  Think of it this way, a big meal at dinner sits in our stomachs overnight.  Also weight loss takes time, be patient and don't expect to see results immediately with this change.  
Best of luck,
Lea

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