This.
Sorry if you have already posted it, but can you put up what you eat on a daily basis. Preferably with a breakdown of cals/protien/carbs/fat.
Are you having your shakes with milk ?
I'm by no means any nutritional expert but I have something like the following which contains plenty of cals in shake form.
650ml milk, 3 large eggs, 1 scoop WPC
Calories: 757
Fat: 32.6g (Saturated 20.2)
Protein: 65.1g
Carbohydrate: 35.3g
650ml milk, 3 large eggs, 1 scoop WPC, 40g Oats
Calories: 909
Fat: 36.1g (Saturated 20.9)
Protein: 70.2g
Carbohydrate: 58g
PS. You think your stuggling. I'm an ectomorph and weigh 87.5KG. Try consuming that much food. haha