Depressed but not Depressed (or not sure)

depression. n - a state of feeling sad, a serious medical condition which a person feels very sad, hopeless, and unimportant and often is unable to live in a normal way

You ever get a sort of numbness but heaviness at the same time? Like something invisible is weighing you down but you can't do anything about it because the numbness is in the way?

I don't know if that's what depression is like but I know that every time I sigh, I definitely feel depressed. In the moment it would feel like for no reason but when you're constantly alone with your thoughts, the cause is evident. Just that the solution isn't obvious, which makes it almost nonexistent, and ultimately, the depression stays and festers; lingering like a parasite, a tapeworm.

Probable causes of my depression:

1. social isolation - I lose friends because I'm too cowardly to ask how they are, and I'm incapable of making new ones because my uni is full of racist, religious supremecists.
2. procrastination - New ideas and projects pop up every day yet I spend all this time playing Clash of Clans and Two Dot.
3. I miss someone - He wasn't my boyfriend but it hurt that he "subtly" showed that he didn't want to have anything to do with me anymore (he had the balls to invite me to his going away party first, though)

I'm an introvert and I have social anxiety.

Why make something when you're not the best anymore?

Closure is unattainable and a rebound is inevitable.

Do people get depression from feeling like an absolute failure?