3 months and not getting bigger means you're not eating enough. And if you're not eating enough, you're probably not really getting any stronger. There is only one way to build muscle mass and that is to eat, eat, eat. Do not bother taking HGH until you fully understand how to diet properly and know the risks and how to do it. I wouldn't recommend it as the human body is fully capable of building muscle mass naturally that will look good.
Working out is the easy part. The difficult part is eating. Anybody can push weight around, but only those disciplined to take countless hours to prepare food and spend the time eating it are the ones who will get size. Do not waste money on supplements either until you are eating. Just as it says "supplement" which means "supplement to a proper diet for your goals."
Put together a spreadsheet of foods you like and find the caloric intake, carbs, protein, and fat. Obviously keep the fat low, carbs, protein and calories high, and put it into a spreadsheet spread over 6-7 meals per day. Once you've done this, if you're not getting enough protein, supplement it with a whey shake. If calories are low, you can take a mass gainer like cytogainer to add a quick 600 calories in one shake (it's like a meal in a shake).
Depending on your size, the numbers you want to use will vary. I started at about 145 and ate at least 5k calories per day, 200g protein and like 900 carbs or something crazy. Lots of chicken, rice, potatoes, veggies, tuna, etc... I put on crazy mass on jumped to over 180 pounds in just months. Many people thought I was on steroids but I had never touched the stuff. I did have a stack of Gaspari sizeon and superpump, and a plain old creatine monohydrate. My bench press over 300 on flat bench and on a hammer strength decline machine I could do insane amounts.
Everybody is different, I'm not saying you'll have the same results, but it sounds like you're not eating. If you had been dieting properly, after 3 months, you would see significant increases in size. Eat all that you can and try to keep it clean. Do not get calories from pop or fast food.
People will give you shit about being on roids when they see how fast you are advancing, but they're just haters who either do not have the knowledge of proper diet, or the discipline. I can't count how many guys I saw at the gym when I first started and in just months they were pushing the same lightweight around and I was killin' it.
I used to have a spreadsheet of my diet, I will see if I can find it if you're interested in seeing what my intake was.
