I’ve got an odd fear about not gaining enough weight?

1. I’m 14 years old and supposed to gain 1-2 lbs every month (depending on height growth), and I’m not sure how I can do that

2. I’m worried that I’m subconsciously trying to stay the same weight the whole month then eat a lot at the beginning of the next one

3. If I was to do that, would the weight I was gaining (I wouldn’t be eating junk food just higher quantities of what I usually eat), would the weight I gained be made up of the same things as the weight I would gain anyway, or would it all be fat

4. Would this be considered an eating disorder?