I was on 1200, 1300 calories a day and shit was happening.
i've been there, let me guess, you stick to it for a few months then the cravings get so bad you could eat your own arm, so you pig out, check the scale and find you have put all the weight you lost back on, so you starve again. yoyoing = bad for metabolism + hormones run rampant.
you need to reduce calories via more cardio + eat more calories. cardio + weights are the only way to burn calories + increase metabolism, dieting alone reduces calories and metabolism.
if you really have stuck to 1200 cals for any length of time, have not piged out at all and still not lost weight then your thyroid is fucked and you need medical assistance.