If your TDEE is 2,800 cals you would have to eat that much just to maintain, at least in theory. On the other hand, if your TDEE is 2,800 cals and you're eating 1,000 - 1,200 cals a day, that's a deficit of 1,600 - 1,800 cals A DAY. Although TDEE can change from day to day depending on level of activity, that kind of caloric deficit I could easily see creating starvation mode.
I'd say focus on eating to maintain for a while and THEN after maybe a month or two of that, try creating a deficit again. But instead of 1,600 - 1,800 calories of deficit EVERY DAY, try something MUCH smaller, like, say... 200? Fat loss will be slow this way, but you won't trigger starvation mode and the loss will be real.