I think the worst part about being clinically depressed is how it feels impossible to do a little bit for a few days at a time, and then all my context/momentum/enthusiasm burns up by the time I come back to a project.
Been there. Luckily my mother managed to drag me kicking and screaming to a psychiatrist as I didn't have the energy. If you can, try to call a parent or a friend and ask for help and be very clear to them that you can't do it alone (I know it's painful to admit).
Turns out I had ADHD and Vyvanse changed my life. I did stop medicating after one year because it wasn't easy on the body (accelerated hearth rate) but medication gave the kickstart necessary to drag my ass through dark times and have impetus. Understanding my problem allowed me to manage it.
