Marko is bang on. I also recommend incorporating legs into your workouts
I can relate to the problem of not finding pants to fit ... despite what you see in my avatar, my legs are not skinny. And just because you're working your legs, that doesn't mean you have to go heavy.
When you're working out your legs, your core heavily comes into play to stabilize (IMHO far more than when you're doing upper body workouts). So work your legs
