If we give you our ideas then it won't be your story. You already have your main theme, so build on that and start brainstorming. I won't give you any ideas, but I will give you advice on how to develop ideas from your main idea.
Firstly, think of your setting. The boy who's struggling in life in a fictional way is very vague. If you want a fictional setting, you can make up a new world or universe or simple make use of the same world we live in but include your own facts to the world, such as technological advancement and so on. If you want to make up a new world, ensure that the world has its own history or mythology that comes into play for the boy and which tie in to his struggles in some way. Make sure to have everything be connected to the main plot. Useless details are meaningless and just take up space.
Next, think of your protagonist. Is he the kind of character who struggles on his own or with friends? Is he an integrated part of society or is he an outcast? Think of his personality and his personal history. Think of what formed him as an individual and how you plan to form him along the course of your story.
Now, think of the antagonist. The antagonist doesn't necessarily have to be one person, although if he's struggling through his life there is obviously a cause, which may be a person. Otherwise, it could be society itself because of the world, history and/or mythology you create or borrow that surrounds him is not compatible with him.
After you've figured out these three key points, try to tie everything together into one big story. You'll undoubtedly have ideas along the way, so make sure to take note of them as you may want to try to incorporate them into your story at a later time.
Remember to write a plan beforehand if you want to write a book. A book is very lengthy and things can drag on. While you write it, you may feel the need to change something, but changing something can change the flow of your story or even render earlier statements nonsensical, effectively ruining the story. Writing a plan will, well, allow you to plan the story appropriately and looking over it quickly can allow you to make some changes if you feel the need to where they would actually make sense.
Good luck with your brainstorming and happy writing.