Can i safely use ambien for sleep, then xanax (alprazolam) during the day for anxiety? can i safely switch between xanax (alprazolam) or ativan if i find one works better?

Your question sounds: like there may not be a prescribing physician involved with this, or at least you don't say anything about the advice of that physician. Benzodiazepines are not necessarily the best treatment for chronic anxiety states like generalized anxiety disorder, panic and especially not PTSD. Antidepressants work without producing tolerance and with much less of a risk of dependency. Talk to the prescriber

You may need a sleep study to determine what treatments will help. Have a complete physical exam to know if these are caused by an illness. If you are cleared please see a Clinical Psychologist with expertise in multiple types of psychotherapy for help with anxiety. Medications should be managed by a Psychiatrist. If you are not confident in your Psychiatrist see another for a second opinion.