Your doctor is committing gross malpractice. Quitting benzos abruptly after taking them regularly can result in seizures and severe withdrawals. The advice to avoid caffeine is a good one, but buspar has done horribly in clinical trials and is generally only used these days as an adjunct to an antidepressant. You need a new doctor, but I would first contact your doctor and tell him to give you a prescription so you can taper off slowly. Then, get a psychiatrist if this is a general doc, but don't ever see this doctor again if you can help it as he knows nothing at all about medication. My own opinion is, if these drugs have been working well for you, the damage of taking them is already done, meaning you're already addicted to them and will have to go through a potentially difficult time to stop them and switch to another medication but you know, if it ain't broke, it doesn't need fixing. If it isn't working all that well, the better thing to do is get into therapy to try and beat this once and for all and as for medication, talk to a psychiatrist about antidepressants, which are no picnic either but do tend to work all the time whereas benzos wear off during the day. If the doc won't give you that refill, then you might very well consider going to the ER, and if it comes to it, I'd threaten the doc with malpractice if that's the only way to do this properly. Good luck and remember, the doc works for you, not the other way around.
How much soda do you drink per day? And how much caffeine is in it? Is that your only caffeine source?