Ovulation between flow and glow are different

So I discovered that on the flow <a href="https://play.google.com/store/apps/details?id=com.glow.android">ovulation app</a> it states I ovulated the 23rd and on glow the 25th I have a 30 day cycle so now I am confused as to which one I should follow I'm 13 dpo on flow and 11 on glow I'm getting negitive pregancy tests so confused any advice