What Causes Early Menstruation After A Gall Bladder Surgery?

i had gallbladder surgery, it went great, i felt fine and went home about 3 hours after waking up from it. the next day i started spotting which was odd due to the fact that my period wasnt supposed to start for another week and im on the pill so its fairly regular. it has now been 14 days of spotting and a period. i stopped for almost a full day and went to go for a walk and ended up starting again so i put in a tampon. in about 10 min it was full. why could this be?