I know this thread is a wee bit old...
AJP - you concieved on a 21 day cycle? How did you know it was that short if you concieved and didn't have AF? Early O? I ask because my cycles are averaging 21 days and I thought they'd be too short to concieve (if I'm Oing it is very soon after AF). Trying to lengthen them, got to 23 days this cycle with Vitex and RRL tea and AF was 1.5 days. Totally left-field.

Sequoia - I heard short cycles can be from high eostrogen levels, more likely if the flo is heavy (not sure that this is true for me b/c AF is quite light). Also, I've heard smokers are more likely to have short cycles, something to do with the chemicals affecting follicular development.

I guess it all depends what end of your cycle has shortened, the FP or the LP- an immature egg or a short LP can both affect TTC. Your cycles haven't got worriesomely short though - 25 days is still considered normal, even 23

ps- when i was taking steroids (prednisone), even at a very low dose, it shortened my cycle right down to 12 days (and 8 day light bleeding yay). If you were very stressed, hypothetically I guess the same thing could happen. I spose b/c the cycles b/c anovulatory. Stress could also shorten your LP in principle. HTH