I'm not tiring to make others feel bad but I'm actually tiring to gain it! I was 5'6" in HS at 121 lbs.....today I'm 5'8" at 121lbs....I haven't gain an ounce since. I eat like crazy! I eat whole cheesy pizzas, burgers, chili cheese fries, milk shakes! everything you can think of! In 2000 I joined the army resv. Drill Sgt. said, "Oh, well beef you up alright!" I got muscle, and nice and cut, but my weight did not change. A trainer at a gym tried giving me some protein shakes but that still did nothing. He gave up on me after a month.
Well you have a really good metabolism. I'm pretty much the same as well. 5'8 145-50. I eat and eat and eat and cant put on weight to save my life. I was told that the more meals you eat a day actually speeds up your metabolism to break the food down faster. So in essence thats why I can't put on wieght. Our bodies just laugh at our feeble attempts to put wieght on as it breaks the food down.