My dr prescribed Lactulose to me. I received it in the mail and it was in a pint sized bottle and half full. I have only been taking it as prescribed for 7 days and am about to run out and can't refill for another 11 days. I am thinking maybe an error on the pharmacy's part. But a pint of Lactulose at 2 tbsp 3 times daily wouldn't last a month. How much should I have received for a month supply?