I agre with Debbie that you need to seek psychiatric help. Family practice physicians and internists are not always trained to recognize psychiatric disorders.
The dry mouth, muscle twitches, numbness, and feeling frightened all the time are symptoms of generalized anxiety disorder. As you have no doubt seen in other posts I've written, depression and anxiety are close cousins. Many people who come to the office complaining of anxiety actually have depression masquerading as its cousin anxiety, which is why this syndrome responds so well to antidepressants.
Benzodiazepines are a risky business, though. If you've ever had any kind of substance addiction problem, benzodiazepines are contraindicated. Although highly effective for pure anxiety, they will make depression worse. Nonetheless, if you have not had addiction problems before, you may be able to benefit from this class of medication, but ONLY if you take them for a very short period of time, and only as directed.
Get yourself in to see a psychiatrist, and do keep in touch. Best of luck to you.
As always, if you feel like harming yourself or anyone else in any way, you must immediately call 911, or go to the nearest emergency room.
Please remember that I cannot make a diagnosis based on internet communication.
Dr. K. Eisele