AF has arrived..

Third cycle of femera down.. No bfp.. AF came today.. My cycles are 28 days every month and I have that in my setting and I adjust it every time glow is wrong and yet the next month it sets it at 24 days my period is expected.. Or 25..never accurate.. When does that adjust itself? It's throwing off my expected fertile days. So aggravating! Moving to digital ovulation sticks this month..