Irregular Cycle... What could be the cause?

I've been having irregular periods for at least the past 2 years. It usually comes around every 3-4 months and is (as expected) very intense. I have taken multiple pregnancy tests, all negative, took one about 2 weeks ago most recently. I have had chlamydia in the past, probably had it for a while before it was treated.. I know I need to go to the gyno, but no health insurance atm and no funds to pay for uninsured. Anyone having/had the same problem and can share what the cause may be?