Hi plz help................want to reduce weight???????

actually m overweight & 19 yrs old &5ft 3" long. i have joined gym to reduce my weight but i am unable to get control on my eating habbits & the day when i decide that i'll not eat bad from today specially that i donot kno what happen & i eat more. its being a month i have joined gym n i have just reduce 1.5 kgs. i dnt kno wht should i do to solve this plz help????????