Fertility friend app?

Is this accurate ? Fertility friend says I ovulated 3 days after my period . My period started the 4th and ended the 10th.. it wasn't a regular period.. I'm usually heavy but it was spotting then heavy then back back spotting. My cycles are normally 35 days long. I had severe cramps on cycle day 17 and by fertility friend I was 5dpo then. By ff I am 8dpo today. Is it possible that I ovulated sooner this cycle ? I've read that it could happen . But just wondering if anyone else has had experiences like this and what was your outcome .