Hi. I just want to talk to people who know what depression feels like so I decided to post my thoughts here. (English isn't my native language so I'm sorry for any mistakes) 
I'm 27 year old. I had studied something I didn't like. I've worked at jobs I hated. The longest I've stayed to the same work environment is 2 years. 
I freak out so easily. Finding a job makes me so nervous. I'm unemployed for 1 year and I feel useless and pathetic. My parents support me. I live with my sister. 
I finally found something I really love and start taking lessons. But I don't feel I'm good enough. 
Im in a  relationship with a very nice guy for almost 7 months. I still feel I'm not enough although he's very understanding. 
One year ago I wanted to die. I'm taking antidepressants and I'm going to therapy. My doctor is very good. 
Why do I keep feeling like this? For almost 3 months I was ok. I was happier, more optimistic, I was thinking about studying abroad. I felt I had a purpose. And suddenly I feel like shit again. I feel useless, empty, alone, sad, guilty without motivation to move on. I don't want to go out. I don't want to attend my classes. I eat so much until I want to throw up. I think about death again. And I harmed myself (not serious injury, I'm too coward for this). Why again? Is this how my life will be from now on? 3 months feeling ok and then back to feeling like this again?