I don't know if this helps, but as you probably know from your studies fat has more than 2x the calories as carbs by weight. If you focused on eating nuts instead of chips your calorie count would go way up. (especially Macadamias, Pecans, and Walnuts.) If you drink milk, make sure it's whole milk. Eggs are high fat and protein. If you eat chips, make sure the aren't "low fat".

I am NOT advising this for everyone, but if you need calories, drink heavy cream. I used to whip it with sweetener and baking cocoa for chocolate whipped cream. Or, just add some cream to your usual milk.

You are struggling, and that's the important part. It's harder for you but you keep doing it. That requires courage.