What's the least amount of calories I can eat without starving myself?

It's super hard for me to lose weight, and I don't know why. Maybe a thyroid problem, idk. But anyway, I'm 15, I'm done growing and I'm 5'1, a couple day ago I weighed myself and the scale said 111, but it seems like anytime I weigh myself I just keep gaining weight, even though I have a 500 calorie deficit a day, so I'm just gonna go with my weight is 111. I really want to lose weight, without having to starve myself, so what's the healthiest and lowest number of calories I should eat a day in order to burn 500 more than I eat?