The joy of weight lose someone help?:)?

so last summer i lost 16 pounds... and i was happy. well i couldnt really see a difference but oh well i went back to school and gained it all back.. thankfully i didnt gain more. but now im at the same again. and ive been trying to lose it.. and i just cant. i go on walks about 4 miles a day. i just turned 17 on tuesday. i weigh 174 lbs. and im 5'4. yuck i know... but i want my senior year to be the best. and i want to lose this healthy. what i usually eat durning the day is. cereal, slimfast, bananas, boiled eggs, 60 calorie pudding, apple, advacado, and thats about it. it depends on the day though. but last year i did so much better and i dont understand why :( please help thanks guys!!