Well, prestiq is desvenlafaxine , which s an SNRI anti depressant , and yes it could have been used for treatig depression , but giving pristiq along with lexapro , another anti depressant is ot adisable and call for more side effects .
Well, xanax can make you drowsy , being a benzodiazepine drug , but not tired , so what you can do is you can take a low dose of say 0.25 mg or 0.5 mg at night only dose , tha will take care of your sleep as well , while assisting the lexpro for treating depression.
However, if your husband does not want you a benzodiazepine such as xanax , then an alternative can be use of a non sedative anti anxiety drug called as buspar ( buspirone ) , which can be used to assist lexapro to treat your depression , without any apprehension regarding making you feell tired ,
Plus , you have to be on these drugs for a few weeks duration till your depression is dealt with after that you shall discontinue them under the guidance of your psychiarist .
I hope this helps..