I am so sorry to read of your husband's heart attack and please know my prayers are with you both.
Do use the Xanax as prescribed as this will help you manage your anxiety and help you in dealing with your multiple problems. And yes, do call your Drs. office today and tell them you need the pain medication. My hubby has had his pain med filled several times after major surgery and no problems other then you must pick up the RX in person for a narcotic as they cannot be faxed to a pharmacy.
This is where you also turn to family and good friends to ask for help especially making the long drive to where your husband is. You must take care of yourself and sometimes turning your worries and fears over to a higher power is the right thing to do.
Sending you many gentle hugs,