JJI actually went through major depression this year and am still going through it for the same reason as Fog. The best advice I can give you is to tell anyone that is close to you and will listen whether it be friends, family, significant others etc. and just rant about things to them. Find some sort of outlet besides tf2 for your feelings. When you tell other people it brings your feelings to the surface, which DOES feel like shit, but you feel a hell of a lot better after you get everything out.
I don't know what is going on in your life right now, but I can tell you that there will be good days and bad days. Some days you will feel on top of the world and others you'll feel like just going into your own corner and hiding. My advice would be to surround yourself with people you love, even in your times where you don't feel like doing it. Also, if you aren't already see a therapist. It may seem like it doesn't help, but sometimes a non-judgmental third party listener can help a lot.
One thing that I did to help me out when I was the most depressed was just to remember a promise that I made to my father before his last couple weeks, that his death would not impact my going to school and his response that no matter what happens he would always be with me regardless. I know this does not necessarily apply to your situation, but I suggest making a promise to your parents/closest person in your life. Something that will help you focus on why you need to go out and live your life and be healthy.
I don't know if any of this will help but I do hope that everything will be ok and that you will defeat your depression. I've been there and still am, so I understand how bad of a state it is. If you ever feel like ranting to someone please feel free to add me. I'm not on very often but I would be more than happy to listen, even if you just feel like venting. This goes for anyone in the thread who is dealing with it currently.
:'( <3 you JJ. Hope things are getting better for you