I am 24 years old married lady,my period started from 20th April and today Is 4th may,my last 3 months date used to come between 15th to 17th and last for 4 days,this month I was worried that my period hadn't are on both dates so I started taking maprate,on third day course my periods started and on the third day I am having pain in stomach and back,is but normal to have periods more than 5 days or I am calculating wrong.