Not eating enough?

I started on 7.5 mg and I am not very hungry. Should I be concern if I only eat between 600-1200 kcal a day? Should I force myself to eat more? For calorie deficit according to chronometer with my age, weight and length I should eat about 1600 cal. I am slightly frustrated because I don’t seem to be losing weight in last couple of weeks, although I lost 4.6 kg last month it all happened suddenly in beginning of the month. Happened last time too, nothing was happening for weeks and suddenly I had lost 4 kg at once.