your posts almost sounds like I wrote it. I have had the same problem since I can remember, about six years old. I am sixty years now and still going through the same thing. Never ending. I have always worked to support myself and it hasn't been easy. Doctor after doctor, I spent so much money with doctors. I honestly i do not believe in doctors. At times everything could be good in my life, having friends and family around and here it comes again for no reason. You never get used to it, it's like death is a moment away. At times I feel as if God is playing some type of game with me, just to see how I react. I tell my son if anything ever happens to me, just know I'm finally happy and my torment is over with. I truly think it does have something to do with the chemicals in our body,but doctors just give you medicine to depend on. Even meds don't help.
Worst of all, I learned not to tell anyone about it anymore, because they just don't understand and really don't give a shit because they never went through it and people just don't care to hear you complain. Well my friends, if anyone gets answers about this, please let us know the answer. At my age it would be nice to have a few years that are left in my life with a little peace.