OP, you see all of these replies and EVERYONE who has experience on this board says the same thing. IT would be VERY irresponsible of any Vet here to give you ANY advice on an AAS cycle since you are only 21. You hear that now.
I was what they might call a hard gainer but I over came it with calories and training. Now I don't recommend this per say, But this is what I did back in my days. I drank three to four milk shakes a day. Of course they had a protein supplement in them and ice cream and peanut butter. But I drank them after or in between meals. I never got fat because of my metabolism. The other thing I did was to carry a small cooler w/ a sandwich, milk or shake and I ate every 2 or at least 2-1/2 hours. I did this no matter where I was.
Keep in mind I was training like a beast with an experienced BB. It was a three on one off routine and extremely demanding.
Now as people have said a good nutritionist, with BB knowledge should be working with you. Take a look at what 3J does on here. See if you can get w/him or someone in the same field. Good luck...