Your muslces should be fine man. I dunno if you just started benching, but when I did I gained pretty slowly. After about 6 months you'll notice a huge difference. If you want to gain muscle fast through hypertrophy, warm up, then do about 4 sets of 12 reps. That is probably what most people would suggest. Also, eat plenty of protein. To determine how much you need, take your weight and multiply it by .7, thats about how many grams of protein you should eat a day when lifting. On your off days, if you're not exercising, I'd suggest eating a little less protein, just because if you don't use it you pee it out, so it would be a waste.
Don't worry about starting small, we all do. I'm about 2.5 weeks away from 17, and usually I'll warm up, then do 4 sets of 12 x 95#. Always warm up too man. It helps to develope your muscle better than you would if you started cold. Warming up is also crucial because it helps to prevent injury, its a good habit to get into.