I'm 37. My cycles are usually on the long side of average - 30 to 35 days or so. I track them with an app, so I do know precisely, but they vary by up to a week and I am fine with that.
This year, however, I have already had two very long cycles. One was 55 days, then I had a normal cycle, and then I was waiting 45 days for my last period. Something similar happened a few times in 2017 too.
I was tested for PCOS a few years ago and I don't have that. Nor do I have any fibroids or anything like that. I'm not getting pregnant and miscarrying - my DH has had a vasectomy. And I am not on any kind of contraceptive or hormone treatment.
I'm not underweight. I'm not overexercising. And I'm not any more stressed than usual.
Could it be perimenopause?