dominikus -
It really is up to you. If you let it affect you, it will. I would recommend making some changes though. "Gaining Mass" if you will. Visually you'll look better and your confidence will shoot through the roof. People will notice, guaranteed. Anyway, below is all the stuff I wrote first, because I totally avoided the question. I think it's for the best though and can be insightful if you're looking to make changes. Keep reading below if you want to read my rant....
**** Start of the Rant/Good Information ****
I'm so happy I read your post, because in highschool I was in the same boat as you. I could eat McDonald's all day long and I wouldn't gain a pound. All the while I hear about people that can't lose a pound if they tried and would have to stay away from certain foods. I just wanted to gain a couple pounds so I would look 'normal'.
Keep in mind everybody's body is different and will respond in a different way to what they eat. There's a whole list of why this occurs, but it mostly comes down to genetics. Look at your father, grandfather, etc. See if they have/had the same build at your age. I'm willing to bet it was the exact same.
So what do you do about it? Believe it or not, what Richard said is spot on. You have to eat alot of protein, GOOD carbs (Whole wheat bread, brown rice, etc.), and GOOD fats (flax oil, fish oil, etc.). You also have a probably have a fast metabolism. So you have to eat A LOT. I'm talking six meals a day, every three hours. Right now, it might seem impossible, but there's plenty of people (including me) out there that do this. There's also a term out there called GOMAD - Gallon Of Milk A Day. If you follow those rules I guarantee you'll throw on some weight. That's only 50% of it though.
What's the other 50%? You got to hit the gym man! Three days a week. You build or find a program online that works for you. There's a reason there's thousands of programs out there. What works for one person, won't work for another. And yes, there's alot of good programs and A LOT of bad programs.
I could give you some sites to get you started, but I'm not sure if I can post links on here. Might be against the 'Terms and Conditions'. So I wouldn't want to abuse anything. If you are serious start out with these search terms on Google:
- Hardgainer (that's what you are)
- Anthony Ellis (the original 'skinny guy')
- Gaining Mass / Building Mass
- GOMAD
That should lead you in the right direction if you are serious about making changes. Let us know if this helped out! ... or if even read the rant for that matter!