Listen, I know in the beginning of this post I was sympathetic to your problem, but I am also here to say, Suck It Up. I can tell you that to gain weight, you need to focus on making your meals a habit rather than an afterthought. Your body is pre-programmed with your genetic disposition. And in your case, you have a very fast metabolism that digests and burns calories quickly. Focus on having 5-6 calorie-dense meals a day spaced 2-3 hours apart so that your body is constantly being provided with something to metabolize and build muscle.
Parashos, S. A., Swearingen, C. J., Biglan, K. M., Bodis-Wollner, I., Liang, G. S., Ross, G. W., Tilley, B. C., and Shulman, L. M. Determinants of the timing of symptomatic treatment in early Parkinson disease: The National Institutes of Health Exploratory Trials in Parkinson Disease (NET-PD) Experience. Arch Neurol. 2009;66(9):1099-1104. View abstract.

Arguably the most influential factor, exercise is what instigates muscle growth. When you exercise, especially if you engage in resistance training, it causes trauma to your muscles. This is exactly what you want because it’s this trauma that triggers a response from your body that grows your muscles. To repair the injury or damage to your muscles, special cells called satellite cells arrive. Typically, your muscle fibers thicken and lengthen in this process. (1)
Stand on one foot with the arch and heel hanging off of the edge of a step or platform. Hold onto something if you need help balancing. Drop your heel all the way down below the step, and then rise all the way up on your toes. Hold dumbbells to make it harder. If you can balance without holding on to something, you’ll work your core muscles, too. You'll also build more stable joints in the other leg.
Many athletes follow a "loading" protocol of around 25 grams a day for five days, but this isn't essential. But as Ciaran Fairman notes in the article "Do I Need to Load With Creatine," you can also get the same benefits with around 5 grams a day, potentially with none of the mild side effects of the loading protocol, which include stomach pain and water weight gain. The catch is that you have to take it consistently. Don't skip it!
Bodybuilders also understand how to diet. This is perhaps the most important aspect other athletes can learn from. I can’t think of any athlete that comes close to bodybuilders who know how to build massive amounts of muscle and then can diet with the type of precision that gets them absolutely shredded on a specific date. Most resistance training sports use weight classes to compete. It doesn’t take a rocket scientist to see that shedding body fat without losing muscle can be a major advantage. Competing at a lower weight class because you are leaner while maintaining strength and performance is a very valuable and effective strategy. Diet to build LEAN muscle to keep weight low for a competitive advantage.

While it'’s okay to chow down on the occasional fast-food choice for convenience, a mass-gain program isn'’t an excuse to gorge on pizza and chocolate sundaes. “"Rebuilding muscle tissue broken down by training requires energy -— in other words, calories,"” says bodybuilding nutritional guru Chris Aceto. "“But many people, including many nutritionists, overestimate the energy needs for gaining mass, encouraging extreme high-calorie intakes. This often leads to an increase in bodyfat, making you bigger, for sure, but also leaving you fat." In general, aim for 300-500 more calories every day than your body burns through exercise and normal functioning (multiply bodyweight by 17). And that'’s divided among six meals a day.
One pilot study using 150mg/kg creatine monohydrate for a five day loading phase followed by maintenance (60mg/kg) for the remainder of the five weeks noted that supplementation was associated with fewer muscle symptoms and complaints alongside improved muscular function,[572] yet a later trial trying to replicate the obsevations using 150mg/kg daily for five weeks noted the opposite, that creatine supplementation exacerbated symptoms.[573] 

The body's pool of creatine can be replenished either from food (or supplements) or through synthesis from precursor amino acids. Dietary sources include beef, tuna, cod, salmon, herring, and pork [2]. The normal dietary intake of creatine is 1-2 g/day, although vegetarians may consume less [3,4]. Dietary creatine is absorbed from the intestines into the bloodstream. If the dietary supply is limited, creatine can be synthesized from the body stores of the amino acids glycine, arginine, and methionine. The kidneys use glycine and arginine to make guanidinoacetate, which the liver methylates to form creatine [1], which is transported to the muscle cells for storage. It is also stored in the kidneys, sperm cells, and brain tissue [5].
To meet the demands of a high-intensity exercise, such as a sprint, muscles derive their energy from a series of reactions involving adenosine triphosphate (ATP), phosphocreatine (PCr), adenosine diphosphate (ADP), and creatine. ATP, the amount of which is relatively constant, provides energy when it releases a phosphate molecule and becomes ADP. ATP is regenerated when PCr donates a phosphate molecule that combines with ADP. Stored PCr can fuel the first 4-5 seconds of a sprint, but another fuel source must provide the energy to sustain the activity. Creatine supplements increase the storage of PCr, thus making more ATP available to fuel the working muscles and enable them to work harder before becoming fatigued [1].
Consuming sufficient high-quality protein is essential for building muscle. Current recommendations are to consume a minimum of 0.8g of protein for each kg of body weight, however, this is really only applicable to the average sedentary individual. Current evidence shows that to support muscle development, protein intake is the key, therefore the recommended 0.8g per kg should be increased to 1.5-2.0g of protein per kg of body weight. For an 80 kg individual, that would equate to 120-160 grams of protein per day.

Collectively the above investigations indicate that creatine supplementation can be an effective strategy to maintain total creatine pool during a rehabilitation period after injury as well as to attenuate muscle damage induced by a prolonged endurance training session. In addition, it seems that creatine can act as an effective antioxidant agent after more intense resistance training sessions.