Sleeping pills, nyquil, etc for friday/saturday nights. That'll really help you get back on track. But make sure you set your alarm for the same time you wake up on weekdays, like I do. That way, you get more used to your sleeping schedule instead of changing it every weekend.
As for the food thing, what's your BMI? If it's changed by 3+ points in the past few years, you might wanna ask a doctor to see if you're diabetic. I like to eat 3 square meals a day with no snacks or sweets (candy, dessert, etc.). Eating apples will help increase your appetite. So will pot. But you might not want to increase your body fat too much if you're still kind of healthy.
Or it could be some kind of femanine hormone thing, like PCOS (although that would cause excess body fat), in which case I have no clue.