need high calorie low fat foods

have you tried cottage cheese. i personally am not a fan but the serving size is 1/2 cup or 4 oz. 116 cal, 5g fat, 3g carb, 14g protein, and 0.3 g of sugar. Cottage cheese can be eaten by itself, on toast, in salads, with fruit or in recipes such as lasagna and various desserts. My 3 year old loves it and helps me make sure she is getting protein since she is not a fan of meat. I also have used it in making lasagne and it's delish!

Maybe you could do some adjustments on some of the foods you are getting your fats from now and look at higher calorie ways of getting that fat in your diet?