im not starving anymore,so im eating more..?

i used to only eat like 800 calories a day,and i finally lost all my weight over a long period of time,and now im 5’2 and weigh
100 pounds and im staying that weight,and i sorta am staying,i drink a lot of diet drinks though,and a lot of water,but now i feel fat for some reason because im eating around a little more than 1000 calories a day but i have a lot of energy eating like this.
heres my eating schedule:
breakfast:packet oatmeal,whole wheat,granola bar,with a lot of protein,1/2 cup of fiber cereal,and some grapes,soon swtiching to strawberries.
lunchh:calorie pack,and an orange,because i dont have a lot of time to eat at school.
get back from school:
i usually go out to eat like subway,and i
dont add any mayo and stuff,just the healthy
green stuff.
snack:skim cheese,or tuna fishh.
but that ones late at night.
i eat based on the 3 hours a day diet,
when you eat every three hours,and im staying
my weight sorta,but will i keep this weight.
is it bad to eat sugar free things at night