Your numbers overall are actually pretty good. Your HDL is high, giving you a TC/HDL ratio of 3.17, which is near ideal. From the numbers you provided, it appears that your triglycerides are only 45, which is great! So I wouldn't worry about your cholesterol if I were you.
As far as gaining weight is concerned, I'm afraid I can't help you with that. But, believe it or not, I was in the exact same position you are in when I was 16. I was about 5'9" and weighed only 115 pounds. I ate everything and anything and still couldn't gain a pound. By the time I graduated high school I was 132 pounds. It took me another 10 years or so before I was up to 145 pounds. And so here I am today at 5'10" and 152 pounds. It took me nearly 30 years, but I'm finally at my ideal weight. And you know what? In a way I feel kind of fortunate, because if I had gained weight easily when I was 16 years old, it's likely that I would be fighting to lose weight today. So try not to worry about it. Actually you're one of the lucky few in the country today. Hey, you don't have to starve yourself to control your weight. In time, your metabolism will change and you WILL begin gaining weight. But until then, just count your blessings and try not to worry about it.