A loss of one pound in a week is statistically meaningless. When people diet often they reduce carbs. A reduction in carbs tends to be a bit, to highly diuretic (very low carb diets are very diuretic). People on very low carb diets will literally pee out 4-6lbs of water over a week--stop the very low carb diet and the diuretic effect stops and the 4-6lbs come back. Virtually all diets tend to lose a few water pounds at the start.
Switching white bread for whole wheat or crackers for bananas is a wise move from a nutrition point-of-view but you are simply exchanging sugar with vitamins + minerals for sugar without. Switching carbs for carbs will do nothing for weight.
A rule of thumb is to lose no more than 2lbs/week. You have a BMI of 25.8. For your age this put you a bit overweight. To be in the bottom 10% (leanest) of your peer group (18 y/o males) (note: do not use adult BMI charts! see:
http://www.calculator.net/pdf/chart-2015.pdf) you could aim for 20% BMI. 20% BMI is right about 154lbs. Therefore if you lose 26lbs you would be in the leanest 10% of your age/gender group. You would not be "ripped" but if you had a "6 pack" it'd be visible.
One would think therefore that if you lost 2lbs/week it would take 13 weeks, and it would except it is extremely unlikely you would/could do it by dieting and you should not try. If you want fast weight loss I'd suggest that you attempt to lose 1lb/week at most, and attempt to exercise 1lb/week. Since 1lb of fat loss requires ~3300C (kilocalories) this will equate to about 6 hours of rowing/week. (Caveat: check with medical practitioner first and if sedentary, it may take 8 or more weeks to work safely up to this level. If you have been aerobically active you could lose 13lbs over 13/weeks "but" you won't. Here's why: If you row you'll build muscles, shoulders, quads, many areas... so over 13 weeks you might gain 4lbs of muscle.
See:
http://www.calculator.net/bmi-calculator.html (for YOUR chart look near the bottom of that page--you do not fit on the adult chart just yet!)
Now for the other 13lbs. Diet. Simple calorie restriction of any kind will work. Using this:
http://www.calculator.net/calorie-calculator.html
We see:
you need 2534 Calories/day to maintain your weight
you need 2034 Calories/day to lose 1 lb per week
you need 1534 Calories/day to lose 2 lb per week
So a 500 calorie reduction/day will meet your goal if you can do 6 hours/week of moderate aerobic exercise, basketball, rowing, cycling, etc.
If you gain 4lbs of muscle to aim for the leanest 10% you'd adjust your goal upwards from 154 to perhaps 158.
Can you do this in 13 weeks. Sure if you are highly motivated.
As for dieting, try fitday.com they have a free tracker which is great. The biggest problem I see is that dieters lie to themselves all the time, by using weighed portions you can track nearly exact calories and also keep an eye on nutrition.
