Menstrual cramps, right time of month, but no bleeding?

First of all, my boyfriend and I have both been sterilized, so the chances of my being pregnant are pretty much nil. I'm 40 years old, and normally get my periods like clockwork. This month, I had my usual cramping...but never any bleeding. I started exercising regularly around 2 weeks ago (I went from 0 exercise to around 45 minutes daily). I know that missed periods are not that uncommon in the world, and wouldn't doubt my sudden daily exercise could have influenced it, but has anyone ever had the usual period cramps, but without the bleeding? Just curious! I'm 40 years old, not overweight, generally healthy. Hopefully it's not the start of perimenopause...lol. Also just had routine bloodwork done at the doctor's, other than a mild vitamin D deficiency, all was normal.