yep. figure out what your body needs to maintain itself, then take in more. 500 calorie increments are as easy as adding 5 pieces of string cheese to your diet, or 5 tablespoons of peanut butter. 500 calories is so easy to add, you won't even realize the addition. spread it out in between your meals if possible for the best effect - it will help keep you anabolic longer.
basically, and you probably already know this, is your body can dig into itself to get energy from fat (fat cells) or carbs (liver or kidneys, i forget which). to get amino acids however, it leaches them from your muscles, making you slightly weaker when you have long periods of not eating. any source of protein added in at timely intervals will keep that from happening, which not only keeps you anabolic (building muscle), but it keeps you stronger.
i don't know your body type, i don't know how active you are, your age, and therefore if what your hormone levels are. i don't know if you have any medical conditions that i need to be aware of, so i will not try to guess how many calories you need. whatever you're eating is obviously not enough, so just add on to your diet.