whats your diet look like? If you really want to add muscle mass as weight. Then get a good protein shake suplement. like 45 grams of protein per serving or higher. Take one erving 1-2hrs before you lift and another serving 30-45mins after you lift. And if you want to one for breakfast. But try not to exceed 1gram of protein per lb of your body weight, per day.
I have a shake thats 55grams of protein per serving, I take 2 day like i said around my workout. Thats 110 grams per day and I weight 198 or so.
I like to keep it at around 1/2 gram per lb body weight for myself. But the pro lifters can take as much as 1.5grams....at that % alot of the protein is wasted anyway.