Why would I be having a 3 week long period?

I'm 26 years old. I have been ually active, however I am positive I was not or am not pregnant. I have been known to have irregular periods and have even skipped a couple twice, but never before has this come up. I started my last period at what was a normal time, although it started out extremely light and spotty for me. As time has progressed over the past few weeks, the flow has slowly gotten heavier and now it's appearing as a normal period except for the rather large clots I have been ping for the past 4 days or so. I also normally have extremely painful cramps which have been absent this time around, thankfully. Unfortunately, I do not have health insurance and with being unemployed, seeing a doctor is almost impossible. Anyone have any ideas?