What you're doing has a high chance of leading to mild malnutrition, but shouldn't be sustained. You're also losing weight too fast. You should be aiming for no

What you're doing has a high chance of leading to mild malnutrition, but shouldn't be sustained. You're also losing weight too fast. You should be aiming for no more than a kilo (roughly 2 pounds) a week. You should (as a general rule) eat when you're hungry, but eat slowly and eat less. After 15 minutes your body's satiation response kicks in and you won't be hungry. Generally for a male in his 20s - 30s less than 1200 calories a day borders on starvation, for inactive people you can get away with 1000. Active people need at least 1500 while dieting, possibly more.