Damn bro, I still have that problem like you do. I don't know why is that. Its probably due to alot of changes, or if you're in a bad mood, lots of things depend on your eating habits, and your diet.
There comes a time, where you can eat all day long, like a horse and after that you can't even force yourself to eat. What I do, I drink alot of whey high calorie protein, or high calorie meal replacement. Try getting Turboflex Meal Replacement. Each serving contains 45 grams of whey protein, and it has around 450 calories. Its a good stuff trust me. At least for us, who have problems like this ..