I'm confused this happen to anyone else??

Gloria
I'm using two different apps and Glow says I'm fertile this week and it's a 7 day of being fertile  and other app says not til next week and it's only 4 days of being fertile, but i have been having like period cramps and little back ache since yesterday and I ended my period on Friday and period is usually 6-7 days and only had it 5 days