I'm in my mid-30s. I've always been thin and had a very high metabolism. I've been doing Stronglifts 5x5 for a little over 3 months. I've increased my weight in each exercise a fair amount over that time. I've taken breaks after running a 10k, and while feeling a little sick, but for the most part I'm sticking with the program.
I eat eggs and salad for breakfast, have a protein shake before lunch, eat beans and potatoes for lunch (or something similar). I try to eat a burger for dinner, but my wife is a vegetarian, "which pretty much makes me a vegetarian", as Samuel L Jackson put it. I eat yogurt and cottage cheese before bed.
I've gained several pounds since starting the program. My muscles feel healthy and firm, but they don't seem any bigger. My gut however has grown enough that it's obvious to others. What's going on with me?
Edit: the comments imply that my question is perceived as "how can I stop gaining weight with this diet". My real question is, why am I not putting on perceivable muscle, though I'm following the workout, and the dietary advice of the workout (which is, for skinny people, essentially "stuff yourself with protein and calories")? My muscles aren't growing but my stomach is, is what it comes down to. And I am increasing the weight often enough that workouts are becoming quite difficult.