Wow, 22.5 BMI. I'd kill for that. Mine hovers at around 26.
It seems what you want is to get more muscular looking. If so, you gotta eat, more protein=more muscle. That's why whey protein exists in it's current form, it allows you to injest more protein without the "empty" calories of food. Whey protein is sorta controversial, not quite as much anymore, but you'd have to do some research and see if you want to take any proteins like that, in just powder form.
I think it's mostly your body type. Assuming you're at 22.5BMI without working out, either your diet is spectacular (which, if you live in Lebanon, it might just be compared to eating frozen pizzas everyday like your typical American diet) or you probably just aren't someone who gains weight very fast, you just got that sort of bodytype.
Basically, you probably should look more into lifting if you wanna get like, ripped or whatever. What happens with some people, if they start when they're fat, and then lose weight, they'll have muscles under the fat and then look cool after losing weight. Like especially leg muscles, get any guy who's like 300 pounds on a leg press, and he'll likely beat you just because he naturally has to hold up more than double your weight everyday he walks anywhere, so if he manages to lose bodyfat, he'll have really muscular legs and lower body in general under his fat. So, yeah, if you wanna look more ripped and whatever, concentrate more on weights.
As far as weights, libraries of books are written about the subject. I like compound lifts, as your muscles will look more natural and they'll have more real life application, I like freeweights better than machines, too, for the most part. As far as specific sports you can get into with weightlifting, there's more or less 3. Bodybuilding, which is lifting with the aim of sculpting a body you think looks nice, competitions are judged by looks, not by weight lifted. Powerlifting, which concentrates on 3 lifts, the deadlift, squat, and bench press, and the maximum numbers lifted in each lift are what you win or lose a competition over, powerlifting isn't about how you look at all. Olympic weightlifting, 2 lifts in Olympic weightlifting now, snatch and clean and jerk. Both of those determine basically how good you are at getting the bar from the ground to above your head in a quick amount of time. Olympic weightlifting isn't terribly popular here in US, but I got no idea about Lebanon. I personally think Olympic lifting is the coolest of all 3, but I suck at it. Olympic weightlifters are BEASTS, like 180 pound guys putting over 400 pounds over their heads... But, look into those and see what you'd like to integrate into what you do for whatever your goals are.
Really, it seems like you might just be what's called a "hard gainer." http://www.muscleandstrength.com/articl ... morph.html If you're an ectomorph, then don't really worry yourself too much.