16 year old weight problems?

I am just turning 16 this month and I'm worried. I am a guy, and I oly weigh between 104-107 pounds. I have always struggled with my weight, but people have told me that I will gain weight while going through puberty. But I'm like the skinniest person alive. And I eat healthily!! For example, my meals yesterday were: 5 swedish pancackes for breakfast, 4 quesadillas for lunch, and MOST of a big Ole' snapper filet for dinner. That's enough right? I mean it may not be overeating, but it certainly is not undernourishment either. People have told me I look anorexic and it is a big confidence problem. It's especially difficult when I see all the other 15 and 16 year olds everywhere and they have like big arms and pectoral muscles and big legs. or at least normal sized for people my age. SO I have two questions: why can't I gain weight even though I seem to eat enough to be normal weight, and what can I do about it?? PLease help!