Welcome to the forum easyrider. Cool name by the way, I love that movie! :)

What you're describing sounds like anxiety/panic to me, which can be from PTSD or one of the lesser anxiety disorders. If it's severe you will need some kind of treatment to have improvement, I don't think it will just go away on its own; and if you really do have PTSD, it definitely won't get any better. CBT (cognitive behaviour therapy) and exposure therapy are commonly used as treatments. Some people also take medication and there are other therapies as well.

I understand being afraid to get a diagnosis but without one it I think it will be difficult for you to get proper treatment. Have you taken this PTSD Diagnostic test:

http://www.ptsdforum.org/forms/ptsd-diagnosis/

If you answer the questions honestly it should give you some indication of whether or not you have PTSD. But it won't be definite unless you see a doctor and get a formal diagnosis. Your choice though of course. Good luck!