Don't take this as a criticism, but I think that's a symptom of low self esteem, along with the other existential questions. And since you're questioning if you have self esteem or not, then you probably don't have...
And vanishing interest in things you usually had interest in indicates 1 of 2 things: depression, or a current major problem in your life that you can't overcome, and so it's natural to lose interest for other things, while that's going on.
I think you need to find something useful to do (studying, working, whatever), so you won't feel you're useless. Do you live alone or with your parents? Either way you have to do something for your future!
But like you said you won't find answers here, if you're having a bad time like you seem to be having, you should see a psychologist. I'm guessing these problems and low self-esteem didn't just pop up, there's something behind that, and a psychologist can help you in the symptoms by going to the cause.

There has to be a drive to do it. I understand that if you, say, write a couple of chapters, show it to someone and they say it's crap, you wanna give up. But if you haven't tried and don't really want to...
