Jake
It seems that the two main causes are psychological (stressed, traumatized, emotional etc.) and physical, like bad circulation.
If so, you should sit silently and work out your issues and go through them so you can reflect on them in a better light (this has happened, but it caused this to happen, it all worked out for the best etc.) and obviously to better your circulation you need to drink pleanty of pure water (not from the tap) and exercise at least 3 times a week byt getting your cardio/heart rate up and keeping it up each session.