Quit its not worth the worry. At the end of the day its only a piece of certificate saying well done you have researched a topic. Its not worth getting that worried about. So quit.

What have you been doing since August to help cope or get over your anxieties? There are numerous things you can try.

I would also add the point that the business world may not present a better situation for you. I don’t want to add to your worries but I feel academia is a good place to be for those individuals that are a little bit nervous/shy/anxious/etc.. What alternatives to academia are you considering?

If you are going to get through your PhD you’ll need to be determined and focus on your work. Don’t waste time and energy worrying about how you’re being perceived, just focus on your work and everything else will take care of itself. At one point you thought doing a PhD was the right thing for you, perhaps you should try to get your head back to that place and stop worrying about everything else!

Hi there again, Angie
thanks for filling out the picture. I guess it's just going to be a really tough decision, but you are just going to have to make one. I find that sometimes the most wearing, energy-consuming and distracting thing about doing a PhD is the constant thinking about if you should quit or stick with it. Once you have made that decision, either way, things will look up!
One thing I sometimes find useful is this: I make a 'provisional' decision. I seriously make up my mind and go about life as if this was definite. But it comes with a time limit and after the time I set myself (a week or so) is over I sit down and ask myself how I felt this week. In a emotional and bodily sense. It's then only after this that I make the final decision. You might want to try this!

Another thought: I honestly believe that if you know exactly why you quit, you will always be able to explain this convincingly to prospective future employers. And quite some might just see that while you do not have a PhD degree, you have a heck of a lot of reflexive knowledge about yourself, your weaknesses and strengths, your motivations, you know what makes you tick and what doesn't and you are able to make hard decisions. This is of high value to employers and might actually give you a competitive advantage if you manage to 'sell' yourself this way!