What Causes Weakness, Diarrhea And Vomiting During Periods?

Im 19 years old for the past few years whenever i hit my menstrual cycle i start feeling weak, light headed, shakey. I throw up and have diarrhea. I also loose my appetite for about 2 days until the pain subsidies...not only am i desperate to find out whats wrong because i dread getting my period each month but im also concerned. A lot of the times i cant get out of bed for 2-3 days. Please help.