I just got my period yesterday?

well yesterday i got my period and it was really early.i normally do not get my period on the first i get it on the 17th or 18th.and i had what i think was cramps sooo bad that i was balled up crying all day until like 4:00 and then it stopped why was it like that the pain was unbarable.that i tought something was like ripping me inside of my bladder