Sedony, I've had something like that myself. It might be related to ovulation. I sometimes get blood-tinged mucus around that time or occasionally, it is rubbery and in one piece. I've often suspected it might be a CM plug which is released when the cervix opens up around the fertile period in the cycle.

I also get cramping around ovulation. The ovary on the chosen side actually "pings" me quite distinctly so I always know when to expect the change to fertile. Apparently, the sharp pains people sometimes feel at ovulation precede the actual egg release by a day or so.

Of course, if AF doesn't turn up after a decent interval, you might want to consult your :doc: