First, it is NOT your last chance in college and you do NOT have to quit your dreams of going to uni even if you DO drop out of college now. There are access courses, distance learning and opportunities to take your A levels again later in life. If you do feel like you have to quit, please try not to see it as a failure. Youre acknowledging you might not be in the right state of mind right now to study effectively and thats a good thing.
What if any help are you getting with your anxiety and depression? Its probably worth focusing on getting the help you need and getting better right now. I know that seems really hard, maybe even impossibile right now, but I promise you its not.
Well done on being accepted into the music project. I imagine this might be something that will do you some good with your anxiety, depression and self esteem. If it does lead you somewhere, great, but whether it does or not, it doesn't mean you have to give up on your other ambitions..