It is 'thinking' that makes you feel that way. In fact you do not need to 'think' at all - or at least you should only think when you want to think and not be involuntarily led down paths of fear and guilt by your mind without even realising it until you are panicking.
You need to control your mind, drugs can of course do this but the best way is through meditation and being aware of your mind. Sound 'new age'? It does have that label but believe me it is the best way to gain control. I am definitely not a 'new age' etc. type of person and years ago I would have laughed at this but it is one of the best things I have ever got into.
Anyway, it's worth reading up on a little and see if you are interested. Here is one to start:
http://www.anxieties.com/gad-step2c.php