This is regarding my menses?

my periods started 2yrs ago. the circle was of 40 days n dey would continue for 7 days. But for the past 1 month the circle has shifted to 28 days just like my mom and periods continue for 7 days and even the pain has increased on first 2 days. My mum gets her period only for 3 days only . why is dis happenning and is there a solution by which my cycle can again become of 40 days?