How do I go about adding calories?
 

I am underweight and am faithfully trying to add the extra calories to my daily diet. So far I've gained about 7 pounds. I need to still put on 15 to 17 pounds.
I've read that I need to add an extra 3500 calories per week to gain a pound on top of what I'm already eating. I make it easier by splitting the 3500 by 7 days and that adds an extra 500 per day to my normal diet. Okay, here is my question, I'm not sure I'll be able to explain. As I put on a pound each week, do I need to calculate the calories needed to maintain that weight and then add the 500 to that, or do I just continue adding on the 500 calories daily to the amount of calories I took in when I first started this weight gain diet.

I'm having some trouble trying to get in enough extra calories as the weight goes up.