im back and have a question

Hello all, I joined back in november after a really long break away but I ended up in hospital with gall stones so have been recovering from my op! Anyway I just downloaded a new period tracker app and i realised that my af has a pattern, one month I bleed for 3 days then the next month I bleed for 2 days then the next month I bbleed for 4 days then 3 again and so on. Ive tracked for the last 12 months and its been the same all through, its very interesting! But im wondering if it affects my fertility at all, weather I would be more or less fertile on certain months if I've bled more or less time. If that makes sense?