This is worth a call today to your provider before you take another dose. Your provider may want you to step off Xanax gradually, replace it with something else, or quit cold turkey - or at the very least they'll want to monitor you closely while taking the drug if, for your case, the risks of stopping outweigh the risks of causing problems for your baby.
Stopping Xanax can cause withdrawal symptoms, so whether you decide together to quit cold turkey or step off gradually, your provider will want to monitor you carefully to minimize any problems that the withdrawal may cause for you or the baby. Xanax is FDA pregnancy category D, which means that it can cause birth defects, but it also may in some cases be safer for some women to continue taking the drug. A doctor or midwife would also be able to give you more information on the chances of a problem considering the dosage and number of times you've taken Xanax.
It doesn't sound like this is true for you, but I say this just in case - Xanax is a prescription only drug but some folks use it without prescription and therefore might be worried to tell a provider about this usage. For the above reasons, I'd suggest if this is the case for anyone you do it anyway - I think your provider will really appreciate your honesty and it can go a long way to building a positive doctor/patient relationship.
I've given you a lot of information here and some of it may seem scary. But consider that some people stay on Xanax during pregnancy with their doctor's okay, so I'm hopeful that you've caught this in time. Great job, mama

Stress is also hard on the baby - so try not to worry too much!