What Causes Period Pain, Nausea, Syncope With Spotting And Back Pain?

Hi I am 20yrs old - i keep getting really bad period pain - for the last nine months (before that ive never had period pain - i stated when i was 11.) It makes me feel nauseous and I faint and am sometimes sick. However it then suddenly disappears after 2 days and i only feel mildly faint - i have had some spotting between periods and some pain on my right side and lower back - any ideas?