Hi, On March I Had My Period On The 10th

Hi, on March i had my period on the 10th and end on the 17th. But in April, i had my period on the 14th but end on the 17th. Which that only last for 3 days. How can that be? I did had unprotected sex on the 8th of March. Then another unprotected sex on the 23 of april. I never have a 3 day periods in my life. During my 3 day of period, it was really heavy on the first day but got light on the second day and completely stop on the 3rd day.