Dude - just my own person opinion - DO NOT - be in a hurry to "gain weight" just for the sake of gaining weight because you think it will make you a barrel chested freedom fighter.
Submitted below, for your review and entertainment, is simply my own experience of "why" it is my recommendation to NOT worry about your weight right now unless you DOCTOR tells you that you need to bulk up.
...your mileage may vary
I am an even 6 foot tall (a little taller if I wear Robert Deniro's silly looking platform shoes) and I only weighed 118 pounds when I joined the Army at 19 years old.
118 pounds soaking wet
in my fucking boxer shorts
...but I could run like a pronghorn antelope being chased by a bionic cheetah.
I ran track and cross country in high school (until I learned about girls and hot rods) and I ate everything that got close enough to stick a fork in it.
By the time I left Airborne School, I was 133 pounds of twisted steel and sex appeal.
When I got to my first permanent party unit, I started doing tae kwon do 4-5 nights a week in addition to the Army PT that I had to do every morning.
NEVER did I adjust my diet to "gain weight" just because I thought it would help me be a better barrel chested freedom fighter. By the time I went to SFAS a few years later, my weight had leveled off at at roughly 155 pounds depending on the time of year and I held that weight for the better part of a decade. I went through SFAS and the SFQC one time and one time only - at a time when folks couldn't stop blathering on about how important it was to be "buff" - and how you wouldn't be able to pass selection and the 'Q' if you were a pencil necked geek but the truth was - being buff never did shit for me as far as contributing to my succes in Special Forces.
I spent 6 months in Haiti eating shitty food - I came home and went right to SERE school and by the time I graduated SERE school, I was back into the high 130's as far as body weight and felt like shit. To recover from SERE school, I went back to doing the same shit I did before SERE school except for a brief period it seemed like I ate everything in sight - but again, my weight leveled off in the mid 150's
I made E7 ahead of my peers and it wasn't because I weighed 190 pounds and was capable of bench pressing 315. Because I wasn't and I couldn't.
It was more likely because I had fooled everybody into thinking I was a good SF guy that knew how to speak my target language, carried my weight and then some when it was needed, excelled at doing my job, demonstrated proficiency with my assigned weapons, and NEVER quit when there was a task to be done.
I spent 3 years in the "school house" and my lifestyle added about 10 pounds that decided to stay with me even after I returned to the line. As I got older and started collecting injuries, it got harder and harder to stay at my fightin' weight.
When I was a 42 year old Master Sergeant, I fractured three vertebrae in my lower back. THAT is when I finally broke that magic 190 pound barrier you seem to be looking for - and I fucking hated it.
I spent 30 days on convalescent leave, then another several months in a back brace. All the while, I was fighting tooth and nail to keep from getting med-boarded out of the Army. It was beyond hard to keep my devastingly sexy dad-bod in the same twisted steel and sex appeal configuration that it was in when I was in my late 20's and early 30's and by the time I made E9, I had just surrendered to the fact that I had collected "injury weight" that I would probably never get rid of because I just couldn't work out as hard and as often as I used to.
The reason Popeye can beat Blutos ass really has nothing to do with spinach - its because Popeye has heart and Bluto is just full of hot air. The size of your "heart" and the amount of intestinal fortitude that you can fit into your guts is FAR more important that how much "muscle" is crammed into your head.
Don't be in a rush to get big - the day WILL COME - when you will wish you weren't - just spend your time just being the toughest god damned version of yourself imaginable.
Just my two cents based on my own rambling experience.