Omg I should've come back to DA sooner to see this!
First of all, I can totally and 100% understand you! I'm 17.5 too XD and I'm in college (in Canada it the step before university) and I'm as lost as you. 
well first thing I can say it that these days designers and game graphists are pretty "important" since the evolution of the gaming industry is progressing at high speed, so you dream got all chance to be fullfiled! I am currently studying medical science because I want to be a "field biologigist". It's not really what I dreamed of but if I had can make a little money to survive, I will write and publish books, I want to be a writer.
So if you want my opinion, it's better to follow your dreams because it's sure that you will succeed with your passion and you will LIKE working! Be one of the greatest of all haha I believe in you! The field of art is rather large, so you have many many chances! 
I can understand that some artists didn't quite made it with their art or weren't able to fully live from their art, but it's a risk to take, The gaming industry keep updating and is getting more and more important so it could be your chance! 
To be fair, I didn't choose to be in science haha my parent chose for me and now they think i would've been  really good in litterature when they read my text, scraps and essays but , between you and me, it's way more easy to find a job and get money from Illustrating a game or digital thing than follow high litterature classes and end up totally on your own with your ideas and papers. 
It may not be enough, but darling the most important part is to feel nice about your choices, don't regret anything, if you choose to go for the commerce, tell yourself that it's also incertain, there is no certitudes in life and there might be a lot of people out there, just like you and me, that are hesitating on the most important choice of ther life. Many people will go in commerce too, for greed, hopes, maybe even passion (who knows?) so there night be a harsh competition out there and if you don't like it, it would be hard to persevere and surpass them, But even if it's hard you can do it, (even tho I wouldn't personnaly choose to follow courses where I'm not confident enough or like at all) there'll be a lot of competition for the jobs at the end and all the best will find their places will those who only succeeded might be looking longer, it's another risk I think might be even to the first. But, If you succeed you can alway earn enough money from it and, in the futur, achieve your dream and become what you ever wanted! Earn enough to live and let your inner artist be reborn, find a job in arts and enjoy it, you can always have your backup studies in any bad condition . Take something you LIKE, even if you're good or bad at it, because you will enjoy it, and whatever you do next is up to you. Be strong, be confident.
I sure hope it'll go good for you darling!
----....I just remembered that you speak French too XD----