I almost didn't respond, due to my history with benzos, but here goes...

4 mg of Xanax, seriously? Is this long term ( more than 2 weeks )?
If so, you are officially in seizure territory should you ever stop or quickly reduce that dosage.
What you should probably expect? If this is taken daily, you will hit tolerance at some point, and 4 mg won't work. You can try updosing, but that won't work. Then you may start having interdose withdrawal, which is the beginning of the descent into Hell.

At some point, you'll have to withdraw, please do it with a doctor's help because you are in danger at that dose. In fact, if a doctor is writing a prescription for that much long term, he should be in jail.

After you are off Xanax, you might still have protracted withdrawal for years to come.
Xanax has been linked to all sorts of brain damage and memory loss, including Alzheimer's. We both have that to look forward to.

Again, please make sure you never abruptly stop taking Xanax. Keep your scripts up to date. There are tons of support groups out there, on the Internet and Facebook. I'm sorry this happened to you. It happened to me, and thousands of others, too.