Where do I start with understanding PTSD? Start with basics.
This one offered a free download on the basics of PTSD
http://www.heartsmovingmountains.com/mm5/merchant.mvc?Store_Code=HMM&Screen=ptsd_basics
Here is another link to start considering ideas to help combat anxiety associated with PTSD
http://www.anxietybc.com/sites/default/files/adult_hmptsd.pdf