I need help, and my problem is I am struggling to reaching my daily calorie intake per day. My daily calorie intake for my weight, height, and age is about 2000 calories if I want to maintain my weight. Right now, I keep falling short of eating around 1500 calories per day and sometimes even 1000 calories per day. This has led me to unintentionally lose some weight, which is bad because I'm skinny as it is already. It's funny because I actually want to gain weight but I can't even meet my daily calorie intake, let alone increase it for weight gain.

Which I know for most people doesn't make any sense or don't understand because would say "Just eat more". Here's the main problem why I can't meet my calorie intake everyday and the reason why I'm somewhat skinny. For some reason, I'm rarely hungry and when I am hungry I can ignore my hunger well. For example, when I wake up in the morning at like 7 or 8 AM, I'm not hungry at all until like 12:00-1:00 PM for lunch time (500 calories). After that I some snacks and water or soda (300 calories), and then dinner which is like (500~1000 calories). At the end of day, I average about 1300~ calories which is really bad and it does add up day by day.

So can someone give me suggestions of foods or stuff that can fill my calorie intake quickly?