MEMORY LOSS / AMNESIA?

OVER THE PAST 6 YEARS I HAVE HAD MANY DYS THAT I FORGET THE VERY NEXT DAY IF SAY TODAY IS MONDAY AND I FORGOT SUNDAY I WILL WAKE UP AND UNTILL I LOOK AT THE CALANDER I THINK IT IS SUNDAY THIS HAPPENS A COUPLE TIMES A MONTH DOES ANYONE HAVE ANY IDEAS BECAUSE NONE OF MY DOCTORS CAN FIGURE THIS OUT AND ALL TESTS HAVE CAME BACK NEG THANKS ASK FOR MORE DETAILS IF YOU NEED