Period that skips a month

So around a year and a half ago my period started skipping a month. The other periods were regular, my cycle was often 50 to 60 days long. I thought it was due to stress, because I was diagnosed with depression around then. Since about last June though my period came back to regular, but really heavy. Then I had a couple of months with 20 day cycles, and my gp had me tested for pcos. She concluded I didn't have it but referred me to an endocrinologist. I'm still waiting for an appointment. Does anyone have any ideas what this might be?