Help im a teen and i need a good diet.?

i am 14 years old and i need a good healthy diet. im around 5 foot 7 and around 11 stone. i go to the gym twice a week for an hour a time, i do pe once a week for an hour and i also do dancing on a saturday morning for 45 minutes, so i dont sit on my back side all the time. i just want to make my diet healthier but there are two problems. one i am very fussy with my foods. i dont like Mushrooms,onions, tomatoes,peppers,melons, or anything like that. my favourite food is all the bad stuff like chocolate,chips and crisps and i have a lot of sugar and chocolate cravings, the other problem is that my mum doesnt agree with me being on a diet, so i still have to eat the stuff she gives me like chips and sausages. so i need to do it kinda sneakily. also am i overweight & do i need to go on a diet? please answer. thankyou so much if you do answer :)