Stomach Pains, Dizziness, Backaches, Vomitting, Weakness. What Could This Be?

Iam Monica, I really would want to know what is wrong with me, Six days after my periods i experienced stomach pains like those i usually experience during my periods,later i started feeling dizzy and had bachaches and i was feeling weak at times,other times i was consitipated and i felt like vommting for two days in the morning. On the day i expected my periods they started and i didnot experience the pain i usualy experience during my periods, it was just abit, the first day the flow was high,the second day it was abit high the third day it was just a little flow but on the same third day i had a terrible backache and felt abit dizzy and that feeling of vommiting.Today is the fourth day i still have this backache and i felt like vommiting in the morning would you kindly advise because i dont know what is wrong with me.Could these be period pains or something else.Please help.