I like to take a rational "first pass" on these kinds of things to quickly rule some stuff out and get set on a path that is going to be helpful. You can work out the details while you're on that path.
To investigate the issue, the first thing you might do is rule out the obvious things like any medications or supplements you might be taking that can have these kinds of side effects. I would hope the medication/supplement angle was already discussed with you by the psychiatrist. Alcohol, drugs, and caffeine consumption are also valid things you can quickly rule out. You might get lucky and it is one of these easily identified causes.
If it isn't any of the above, and the issue persists, you have a number of options. Medication: the xanax is a good pill that works well when used when you really need it. Used too often, it will lead to the development of tolerance and it's ugly cousin, withdrawal symptoms. If you haven't already researched it, lexapro is an ssri (antidepressant) that is to be taken per the prescribers' dosing schedule. People do get some anxiolytic benefits from anti-depressants. Be aware that any medication comes with it's own side effects and regularly taken ones usually have withdrawal symptoms should you decide to stop taking them. Depending on how severely the attacks impede your daily functioning, those risks may be worth taking.
Another option available to you is therapy. This option might help sort through any contextual factors and give you some tools to manage or lessen the frequency of attacks. Therapy is available from a number of different sorts of practitioners with different backgrounds, different credentials, and different approaches. Common therapy modalities include behavioral, cognitive, cognitive-behavioral, and the less well known psychodynamic. All forms have evidence for efficacy. You may personally prefer one form over another and find it more effective for you. If you decide on a therapist, I would recommend seeing one with a doctorate in clinical psychology. They will have the best scientific background along with extensive training and experience in therapy.
Finally, alternative but efficacious approaches also exist and can be beneficial. Regular, intense exercise is great for both anxiety and depression. Certain spiritual work, whether you treat it religiously or not, has also been shown to be efficacious. Examples here include yoga and meditation. If you are religious, prayer and social support from your religious community will also be of benefit.
This is just a small taste of the resources out there. Let me know if you have any additional questions.