If you mean to win on a state level as a heavyweight, IMO you wont do it without steroids. I think its a harsh reality, you can believe it or not, but like I said, I think your cousin has a secret.
Depending on your relationship with him he may be honest about it. If you are of the mind that steroids are a big bad evil thing and that I'm saying your cousin is a loser, well thats not at all what I'm saying, so I hope thats not the case. Just like MANY drugs, there are lots of lies and misconceptions about steroids, at best what you think you may know are worst case scenarios. I have even heard that steroids give you bad breath which I find amusing as well as stupid.
Are you 14 years old? You dont have your birthday listed. Obviously at such an age even thinking about it would be the wrong thing to do, I can tell you I knew someone who used around that age and he ended up very, very short. I would think that him being 30 or 31 by now, that he probably regrets it, but who knows. When you first start out and when you are young, you should make great gains for awhile. When I was in high school adding 5-10 pounds on your bench a week was not abnormal at all.
No matter drugs or not though, one thing is for sure, diet is going to be neccessary to carry somewhat large amounts of muscle. Your meat (protein) cannot be sustained without, protein.