Why Is My Stomach Getting Bigger?

Hey Ive Been Doing Turbo Jam For About Three Weeks Now. I Love It And Its Really Making Me Sweat. The Thing Is After I Workout I Measure Myself And Ive Noticed That My Stomach Has Gotten Bigger. I Got Turbo Jam Off Of Amazon I Have No Clue On What Her Eating Plan Is So I Haven't Been Dieting. Most Days I Eat Normal Foods But Small Portions And Alot Of Sweets. Other Days I Would Try To Eat Healthy And Not Eat Alot. Ive Never Been Able To Eat Enough Calories (1200). Please Help Me To Get A Daily Eating Plan And Advice On Making My Stomach Go Down Instead Of Up.