Autism and Food

Okay so, i need help. Badly. I'm a mere minor, but i am 100/86 lbs over weight and i need to go on a deficit as recommended but the thing isss, it's not that I'm eating too much, I'm eating too little and don't move around much. As someone with AuDHD i know all too well about "safe foods" and i have ONE specific food that has never failed me. I eat only that. Its those square pizzas from Walmart ifykyk. And it's only once a day, nothing additional to it, and i drink a lot of water I can't stand sugary drinks so thats not a problem for me, and every once in a while i have a snack throughout the week. I genuinely don't know what to do, I can't stand to eat most foods, if i try, I'll literally vomit. I don't know how I'm going to lose weight or get healthy when I can't handle foods that have protein other than chicken, and all the other good foods or whatever with vitamins and stuff. I have been gradually doing better at moving around, but with little energy i have due to barely eating I can't move around much without getting headaches and feeling overwhelmed. What do i do?

Side note: when i say I'm picky, I mean PICKY. So picky that the most i'd eat are 3 maybe 4 foods on repeat if i have to, if i don't, it'll be 1 food only, and that 1 food would be my squares pizzas. 😭