You have nuts putting yourself out there like that. But listen to these guys please. AAS could exasperate your problem. Your diet completely ruined you. Processed foods are the worst thing to happen to humanity since small pox... no joke. Frozen pizza and soda are the absolute worst things you can put into your body. You are correct about having low testosterone. Hormones require real foods to be produced. That diet has ruined EVERY SYSTEM IN YOUR BODY. EVERYTHING. You probably have a slough of other problems that have yet to manifest symptoms, or you just don't notice anymore.
I have good news for you however. The human body is an incredible thing, and you are young so there is hope.
The bad news: You have to make a lifestyle change. Sounds like you are already on your way, do what your trainer tells you. Study nutrition and exercise religiously. No more video games, get a real job... one that gives you health insurance. And don't bs yourself , McDonalds will give health insurance to full time employees. Get outdoor hobbies, play rec sports, read books.
In time you will be ready to cycle, but you have some work to do to heal your body and I'm sure much bigger problems to deal with at the moment.
Get squared away before you take the plunge, or you will net nothing from the experience. Good luck.