Oh no no no! You don't want to play doctor with this for a bunch of reasons. For one, you're talking about two totally different meds. Paxil is an antidepressant, and Xanax is a benzodiazepine. They cannot "replace" one another, they do totally different things.
Do you not have a refill of the Paxil? If not, you need to contact your doc ASAP and obtain at least enough of the Paxil to get to into see your doc for a refill. Stopping Paxil abruptly can be a nightmare.
I also want to caution you that it's never a good idea to hang onto meds and try to doctor yourself with them, especially strong, potent, habit forming meds like Xanax. Is it YOUR medication? If you don't take it anymore, it should be properly disposed of. Unfortunately, a lot of people get into the habit of hanging onto unused Rx'es, which leads to a lot of diversion. The #1 way teens and young people obtain meds to abuse is by raiding the med cabinet.
Please do this the right way and get a hold of your doctor so you can continue to take your Paxil as prescribed. Even on a weekend, there will be a doctor on call.
Let us know how you're doing!
Sorry, but you must ask your doctor about this. We are not doctors, so not allowed to answer your question. Blessings - Blu