It's an evolutionary reality that your body gets alarmed when there is a big, sustained drop in calories. If you are sedentary, your metabolism slows down to preserve energy. Two things might help - one is getting more exercise. I'm older and not a gym rat, so my exercise is simply walking. It took time to get up from a miserable half hour to a much less miserable hour-and-a-half a couple times a week, but it makes a huge difference in my weight loss. The other is what is called zig-zag dieting. Low cals several days in a row and then a more weight maintaining level for a day so your body calorie deficit alarm isn't going off. I'm not saying drink soda on the zag day, but give yourself a little slack to eat a sandwich or a fruit cup.