First, let me tell you this:
Do not eat any form of fast-food shit. (pardon me for the curse)
If you go on a binge diet to gain weight that way you will be worse off than you started.
I would suggest that you look into making protein-shakes such as:
find a decently priced whey protein take 4-scoops of this, take a pound of strawberries, 6oz of blueberry'raspberry'blackberry and about a half pound of cherries.
this will produce roughly 2,500 calories, in a 48-ounce drink. If you want you can eat what you do normally but drink half of this shake per day.
I cannot tell you this will help you in what you are wanting to achieve. But I believe this may be a plausible solution. If you take half-per day you would be adding about 1,300 extra calories.
Throughout life there are bumps along the way some may be painful...others not...who gives a damn in the end you'll still die