How to control extreme mood swings?

Earlier today I was about to jump off the balcony. I already had my note written and was standing on the railing. Then I asked myself "what the hell am I doing?" And I got down and tore up the note. Now just an hour later im sleepy and content. Im not sure im ready to die yet but often times I think otherwise. I really dont want to do something id regret later, but I fear soon it will be too late. my counselor diagnosed me with extreme anxiety, depression, and borderline anorexia, but im not sure if that has anything to do with it. Im only 13, too young for this...