What Causes Irregular Periods?

Hi, i am 32years old & have period cycle problem.. am unmarried but it is planned in couple of next weeks... issue is my periods are irregular from last 3-4months..... & last two mnths it wasn't started and it started after 45days & now not stopping (flow is very less), its worry for me since i am getting married in couple of weeks now... please advice...i have done sonography & seems was some problem... i lost the report & will get it done again... still pla suggesy why is it happening?