The trouble you're experiencing is probably to do with your bodies expectations. Try upsetting your bodies normal routine. I've heard the best way to gain weight is to try and eat nothing during the first half of the day. Absolutely no breakfast, your metabolism thrives on it, then in the evening, as late as possible, eat all you can. Don't eat too fast, try and spread it out over a couple of hours that way you'll be able to fit more in. Having a huge amount of the food in the evening is as good as eating in your sleep.
Also try eating less every second day. Gorge one day; fast the next. You need to persuade your body to store fat rather than burn it. Nuts are a great source of good fats and will still make you put on weight like animal fats. Don't neglect your carbs remember pasta is great for weight gain, if you eat it in large amounts.
You might also want to try actually setting an alarm to get up in the middle of the night to have a big snack and then go back to bed stuffed. Your body wouldn't know what hit it.
16 years
