Have you considered that you might have an anxiety problem?
You mention being crippled by fear. You mention a constant gnawing. You mention a daily rehearsal of a major anxiety, your always feeling behind, frequently feeling exhausted and terrified, an endless state of panic, and being endlessly haunted. That is a whole lot of anxiety, and there are other kinds of anxiety disorder besides social anxiety.
My tip for you: find a therapist you like and go regularly. You've got two problems here: you are trapped in a behavioral loop, struggling for context. And, being young, you don't have enough life experience to see as many patterns as somebody older, especially somebody who spends all day talking with people. Regularly seeing a good therapist will help with both of those. They can also help you consider whether your level of anxiety is unusual, and what your options are.
I should add that when I was your age, I was too arrogant to do that. I was sure that by dint of raw smarts I would figure it out on my own. Which was both true and dumb: reinventing psychology from scratch would in some sense be an achievement, but like most reinventing of the wheel, it's not an achievement that anybody cares about, not even me.
Anyhow, I have worked out an anxiety-related checklist over time. Now when I notice anxious feelings, the things I wonder:
* Am I getting enough exercise? 30-60 mins cardio 3-4x week is about right for me.
* Am I carrying a lot of stress in my body? Yoga, massage, and hot tubs are helpful.
* Are there environmental factors? E.g., noisy environment, messy living space.
* What am I eating? My mood is most stable on foods with low glycemic index, worst with junk food.
* Am I getting enough sleep? I do best with ~7.5 hours on a very regular schedule.
* What's my drug intake? More than 100mg caffeine or 2 drinks alcohol and my mood will be less stable the next day.
* Am I taking my vitamins? This could be placebo, but I take a B-100, a sublingual B12, and some fish oil. My doctor recommended them for reducing the effects of stress.
For me, my procrastination is directly driven by feelings of anxiety. The more chill I am, the more I get done.