From what I've read that is not really the short they are talking about regarding menopause, that short is like a 7 or 8 day follicular phase. I think Oing at about CD12 is more of a normal variation on the 28 day/O on CD14 cycle, a normal cycle that is is just a bit shorter than average.
I'd agree with this.

That said, if it is really worrying you, you could get your AMH and/or CD3 FSH tested to assess your ovarian reserve.