What is the matter with me?

the 28th of may was the begining of my last period. it lasted until the 10th which isnt normal for me as it was heavyer and my periods only usually last for about 5 days. then last thirsd i had ay the worst cramp in my lower belly and back that lasted about 3 minutes, this happened again the next day while i was out shopping and i couldnt walk cause it hurt that much.it has been fine ever since i dont know if it has anything to do with my extra long period. has anyone experienced this before and what was the outcome, i know it is probably nothing but dont want to go to my GP if nothing is wrong :D