Losing Weight too fast

hi,

so i'm worried i'm actually losing weight too fast!!

i only started this on Monday (1200-1300cal p/day & 30 minutes of Jillian Michaels ripped in 30 per day) and in 4 days i've lost 1kg (2lb)!
Im only 157cm tall and now currently weigh 53.6kg. My goal is 52kg and if i keep this up ill be at my goal in a couple of weeks or less!

Over the past year i have SLOWLY lost 7kgs just by jogging and am now smack back in the middle of my healthy bmi.
I worry as i know that if it comes of too quickly, that its likely to go back on quickly again too.