Feeling bad for failing at something is not depressed. If you were really depressed, you would probably not even have tried in the first place.
I do want to give up and stop trying, but I end up forcing myself to do things (it makes me want to bash my head against a wall until I knock myself unconscious, but at least I'm trying to work through it)
That's still not really depression, if you were despressed like martinuz said you wouldn't of tried. You usually wouldn't even think of trying. Depression is waking up and seeing the pile of work before you, then shrugging and going back to bed/reading a book/staring at the wall before you go to lay down for the night so you can get up and barely even exist the next day.
Depression is also a constant, there isn't something that makes your days bad, they just are bad. Sometimes they are worse sure but usually they are just bad.
That said I'd love to offer positive advice on what's making you feel sad and the bad feelings you do have but as someone struggling with depression so bad I haven't properly cleaned my room in a year I don't think I have any advice to give.
If all this makes you angry at me though and want to tell me how you do have depression, go talk to your doctor. Depending on where you live anti-depressants are pretty standard stuff.