How old are you? I know of few people in this generation who haven't gone through deep lows of depression & stress & anxiety in their teenage years.
Speaking as a psychology major, I can tell you that the solution to your problems is heavily dependent on who you are, your own situations, people around you, etc. However, a few general things that are repeatedly proven to help:
--Exercise: The relationship between the physical & the mental is so often undervalued. The brain is a physical structure, and getting heart rate increased really fuels the brain, releases positive neurotransmitters, and does a whole host of cool things that are really interesting from a psychological perspective, all of which lead to mood elevation & stability.
--Variety: Whatever you're doing, do something different. Try cooking a new, simple recipe; take a drive to a lake you haven't seen before; read a new kind of book, watch an exciting movie, do things to kick you out of a narrow thought process.
--Talk with people: About anything. Depending on the person, you may want to tell them about your struggles, and I pray that you find someone you can have this discussion with. However, even if it's just about cars, or hockey, or cats, or any topic that interests you, being with good people is a very useful tool.
--Anything that gives you a sense of accomplishment: The notion of wanting to die is logically founded on the notion that we aren't doing much while alive. Everything I do is wrong; nobody likes me; I'm worthless; find something to fight for, and put your heart & soul into it.
As I was writing this, I saw you say it's from a chemical imbalance. I worked with a girl over the summer who had the same situation; every morning, she woke up with depression. She is the most Christian girl I know (only 15!), considering becoming a nun, and wants to be an elementary school counselor for kids with depression & anxiety. Thank God for what you're going through; it's hard, but I promise He'll reveal some blessings when you say "I don't know why, but thank you." She's using her situation for incredible things; if you're being called to be a missionary, that'll accomplish everything I put on this list, and fulfilling your calling from God is the best way to find accomplishment.
God be with you; thank you for being brave enough to post your situation in this forum.