i agree with your dad. When i was losing weight before i lost like 2 pounds every week and i was having like 1600 cals. then i reduced to 1500, 1400 and 1300. Dont go below 1200 it lowers your metabolism. Also increase exercise if possible. I know how you feel about eating sandwhiches. I used to feel so secretly pissed off at my friends at lunchtime cause id be eating rice cakes and they were all skinny and eating hot lasagne, coke and chocolates. Hooe this helps!