How do I turn my brain off?

My brain doesn't stop. Even when I'm sleeping I feel like it is still in Autopilot. I can't remember the last time I had a good and restful sleep, or the last time I slept through the night. Or even the last time I slept at night. I often fall asleep at 4 or 5am and sometimes am awake by 8 or 9am. If the thoughts were not intrusive it probably wouldn't bother me so much, but my thoughts are a constant buzzing ball of energy full of fears, and regrets, and disappointments. They make my mind race, sometimes triggering my heart to race, and often making me spiral into a depth of despair. The knots sit in my chest and in the pit of my stomach, and the feeling of being afraid doesn't ever leave. I am afraid of everything, and nothing all at once. What tomorrow holds, even before tomorrow comes. Pre-empting the bad stuff without the presence of anything bad. If something good or positive happens, I question it. Because nothing really good ever happens to me. Not without it being ripped away suddenly or turning into something bad. It is like I am preparing myself for the bad so when it happens I can tell myself I knew it was coming anyway. Why don't I take antidepressants? Well I have in the past, and it numbs all parts of me. It quietens the fears, but also quietens the good stuff, and I don't like feeling I have no stuff at all. No bad, no good, no anything, and when the good parts of me come out, I actually like them. I like the fun side, the spontaneous and loving and caring me. I like the slightly crazy, intelligent, and chameleon me. The I will try anything at least once me. The open minded, expressive and straight forward me. The non judgmental me. They aren't always around, but when they are I like them. When I take the pills it all stops. All of it. And I find myself missing what it's like to feel again. To cry real tears when my dogs died. To laugh real deep belly laughs when I find something funny. To taste food when I eat it. To be able to feel and not go through the daily motions as if I am in a robotic state. I miss the empathy I feel and the opinions I have and the expressions I voice. But the dark side is also real, and there are days I can't function because it's there. Sitting inside of me slowly eating at my soul, and constantly reassuring me that I need to always feel the fear. Because the second I stop feeling the fear, life is going to explode in my face, and remind me there is so much to be afraid of. I wish I could turn my brain off, but only some parts. The parts that allow the fear to take over my mind and body and entire existence. The parts that make me long for internal peace, when all I see is darkness.