Have Irregular Period, More Pain. Had Ultrasound Sound Test Done. What To Do?

Hie, im 26 years old. every since i started my period at 13, i period was always clockwork, spoton 33days. but when i moved back to my home country 2.5 years ago, it became haphazard. now i barely know when my period is coming, it comes anytime between day 28 and 40. i had tests done before because the intensity of my period pain increased intensely painkillers just dont seem to work anymore. i had an ultrasound sound done and they found a cyst in my ovary but it went away. last month my cycle was 31 days, 28 days before and 40 this month.

What is happeneing to me?