DO NOT weigh yourself during the day and weigh yourself once a week max!
if your controlling your weight, pick a morning, I personally weight every Sunday morning, after visiting the little girls room and wearing the same stuff to be as accurate as possible.
Now with you gaining weight, Im afraid my dear its sounds like, like me, youll have to be aware of your intake and expenditure for the forseeable future to maintain the weight you want.
You are indeed only young and not eating enough will hinder your bodys attempt to grow and can damage you metabolism and affect the rate in which it burns calories.
Sure, we'd all love to eat what we want and however much we want without it affecting out weight, but that sad matter of fact is that isnt the case.
The chocolate and crisps are the avarage, but shouldnt be normal.
Todays society eats these things with out realising the little or bad nutrition that is within them.
Remember treats are good, but in moderation.
You may have a simular problem as I, which is finding a balance between losing weight and maintaining that.
MOST people who lose weight, tend to put it back on as well as gaining weight! simply because these people see 'dieting' as the answer and once they have lost the desired weight, they will go back to the way they originally ate which led them to GAIN weight, not stay the same.
Write down the foods in which you lost weight on.
and add a few things to that, say that you had a plain sandwich for lunch, add salad to it, on the side something good for you like an apple and say if your a crisps person add that one treat to that meal.
Id recommend that you make your diet healthier and have treats in moderation.
On the exercise side, Im not so informed on, what I do know is that exercise, for weight loss and to benefit you respiratory and cardiovascular system would be cardio, which involves you warming up, stretching and working out(wether it joggin, dancing etc) with a heart rate elivated at a constant for no more than an hour each period each day, you can do more messing about with your friends and such, but not for physiological purposes.
So running on the spot for a few minutes prob isnt very benefical if it really is only a few minutes. Walking: fast paced to elivate heart rate.
I recommend swimming as the isnt the joint strain there is with jogging and it can work out alot of the muscles in your body.
jogging increases your heart rate(remember this can be unsafe if your alone)
and cycling!
Press ups come under resistance training, which is fine, but realise your not burning calories(energy unit) that way, your increasing muscle mass on your arms, mscle mass can make you weight more, but this isnt a bad thing, the more muscle you have, the more efficient your body if at buring those calories, youll appear leaner and become stronger too.
with push-ups as they are resistance trainging dont do them everyday.
once every 3days is sufficent, as you need time for the muscle, this also applies to sit-ups/crunches.
With resistance training only work one group of muscles every 2-3days.
example, monday-stomach, tuesday-arms, wednesday-legs/thighs, thursday-stomach, friday-arms, saturday-legs/thighs, sunday rest.
well you get the picture.
I think you shoudl use work on becoming an healthier person and finding the balance!
Good luck