Already mentioned it but I would highly suggest to anyone to take St. Johns Wort. It's a herbal remedy that *can* help. It's not a cure-all but for me and a few of my friends, it's helped a decent amount and it's really cheap too. I get it at Sunflower market for 7$. Only thing though is if you're female and you take birth control, it can fuck it up.
Whenever I was in my teens I was EXTREMELY depressed. Like, I could be with all my friends and be even more lonely then if I was alone. I would google suicide and see what came up and one thing that did that I'm pretty sure saved my life was a pretty plain website that just had a few paragraphs and the person just wrote how much they loved me and how important I was. actually, this is the website:
http://www.metanoia.org/suicide/
That and Bjork were my life-lines in highschool. It's definitely a process. Just everyday tell yourself you're awesome or you love yourself. I would scream in my car on the freeway "I fucking love me! I'm amazing! I'm fucking amazing!" and just pump myself up. Even if you don't believe it now, if you keep on telling yourself it and repeating it, you'll start to believe it and trust yourself. Be as egotistical and narcissistic as you want. If any sort of negatives come up. Fuck the negatives. If someone doesn't like me for X reason, fuck them, they have no place in my life. If X is a fault I have, fuck that fault. I'm not gunna let it get me down. I'm stronger and better than that! REFUSE to let some garbage emotion control you. YOU control you! You're fucking awesome!