What Causes Dizziness,cramps And Fainting During Periods?

Hello, i wanted some information on periods. I'm 18 and each time when it comes to the time of the month i get dizzy alot and get really bad cramps. sometimes i also end up fainting. is this normal? the pains that i get be soo intense that at times i cant even walk. also recently I'm starting to get really bad back pains that come all the way round my waist and a pulling feeling from the vagina that seems to pull. i have another 2 weeks for my next period date but yet am getting these pains. what could be the cause of this?