i have the same problem as you and it is very worying,have had this now for about 6 years it does get easyer in the fact that you learn to relize the symptoms and learn how to control them.
worrying dosnt help the matter as you often get cold sweets and a few times i have ended up getting up in the night and feeling sick and shaking with the pain in my chest.i find haveing a cup of tea and two paracetamole help to relieve the pain and after about an hour can go back to bed and sleep.
hope this helps
alan