Hi Depression_here,
I am so sorry for what you are going through. I know how hard it is to be young and struggling with depression. It isn't easy, I know. I had to deal with that too.
Do you have a family doctor that you can see? I would recommend talking to him. Maybe getting a physical and make sure there isn't anything else going on. Also you could let them know that you are depressed and they might hook you up with some medication or counseling.
Another thought might be to talk to your school counselor. They can be very helpful.
What kind of activities do you like? There are many things that you can do to meet other people and maybe make some new friends. That is always an option. I know that it is har d to lose friends that you have known for a long time, but there is a lot of living for you yet to do and you will meet many new people.
Why dont' you just go to chruch on your own. I am sure when you are there that your friends will talk to you. You don't need an invitation, just go.
Here are some resources for you to check out:
http://www.teencentral.net/
http://nineline.org/
http://forums.teenhelp.org/
http://www.teenhut.net/
http://teencentral.net/
I hope that this helps you some. Keep posting, as we are all here for you.
Hugs, Karen