Talk to Gynecologist on Periods Cramps

I am having my menstrual cycle since last 10 years and never have my periods cramps. Not even for once. But in this month of July when I go through that cycle I have severe cramps that were so painful that I can't even stand and move during my periods I have pyrexia and am taking medicine of that. Am those cramps didn't stop after 3 days they were long till my 6th day I can't take medicine for this but if it will happen again in August I surly can't move and am a student I have a lot to do can't just bed rest myself plz suggest something . thanks in anticipation