Not eating enough?
This sounds dangeriously low on kcal and nutritional value. I would for starters recommend you that when its hard for you to eat more to atleast supplement urself with vitamins. Those arent calories so you wont get fat. And it will help your body!
Nuts - protein and healthy fats
If you're feeling tired you're not getting enough carbohydrates. Your bodies main source of energy comes from carbs. If you're consuming a low amount of carbs your body will start to turn the protein you eat into glycogen which Is energy stored in your muscle tissue and liver. When you eat carbs it will do 1 on 3 things 1st if your body needs energy right away it will use the carbs to make glucose (blood suger) this will in turn spike your insulin levels which is an anabolic growth hormone that helps store protein and carbs into your muscles etc 2ndly if energy is not needed immediately it will the turn the carbs into glycogen which is stored in your muscles and liver (as I stated previously) 3rd if your glycogen levels are full and your body doesn't need energy only then will it store the carbs into fat through a process (if i remeber rightly)called trioglocen. So basically eat carbs for energy low carb diets are in my opinion pointless