Glow an my fertile period

So last month Glow predicted my cycle length was 40 days an I started right on the day it said. However I normally have a 30-33 days cycle an its putting me out 49 days again... My question is as for my fertile period do I follow glow bcuz I'm hurting like something is going on near my ovaries I'm on 1600mg vitex daily since last month just natures way brand this month ....