painful period and irregular period problem

anybody knows what cause painful during in period time? also anybody knows what cause irregulare period?
I have these problems since I gotten my first period until today. I get my first period when I was 20 years old and now I am 22 years old. but I never get regular period. sometime can take 3 months without periods. then when period come I have so much pain.
any medicine to take for this problems? or? I am virgin.


thanks