Cycle trend

I have been charting since March, TTC since June. I just started my period again, and I realized that every other cycle is shorter. I'll have one that is 25-27 days and then the next is 33-38 days, then another 25-27, and back up to 33-38.

I'm wondering if there's any significance in this trend or how it helps me trying to get pregnant. I've been using opk's so i'm not worried about missing the window, just trying to learn and understand more. Anyone have any thoughts?