HELP PERIOD IS MESSED UP

Okay so last week on Tuesday I started my period, that same day I went to the doctor and he started me on the pill (levlin) and iron tablets due to EXTREMELY low iron... so I started taking the pill and iron that day and he said the pill would make my periods lighter and shorter but THE ACTUAL COMPLETE OPPOSITE HAS HAPPENED IT IS THE SECOND SATURDAY SINCE I STARTED MY PERIOD AND IT IS STILL HANGING AROUND!!! That means I’m on the 13th day... Normally my periods last from 7-8 days...

I also have incredibly painful cramps... What should I do?? I’m high-key stressing....also 16yo virgin i dunno if that means anything