Over the last few years my cyles have become shorter. Used to always be 28 days now they are commonly 23-26 days, sometimes 27 or 28. My last cycle was 20 days. In my case it probably is peri menopause as I'm 43.
Even so I still managed to conceive 3 times in a 12 month period. I found it always happened when I managed to O on day 12 or 13 of the cycle. Most cycles I O'd on CD 15 or 16 & with a shortish LP of only 11 or 12 days that didn't leave much time for things to develop.
I was lucky enough to have it happen naturally but a FS can manipulate your cycle in order to achieve a pregnancy. It seems that it's all about timing.
ME 43
DS 14 months