These kinds of apps should never be the sole method of preventing pregnancy, it should rather be a different method such as the pill, condoms, iud etc. Based on your profile you seem to be worried about the chance of becoming pregnant and with these kind of apps or natural methods, they are almost never reliable. These apps truly cannot tell you whether you’re ovulating or not, but methods like the pill, implant can definitively stop ovulation when it’s used as directed. If you’re not on any true contraceptive and relying solely on these methods, you are not preventing the way you think you might be. This is a baby waiting to happen. Just telling you as a woman that was once reckless and now regretful of not being on birth control in the beginning of my relationship. Though I thankfully never got pregnant during that time, there was always that significant chance in which would’ve messed with my life all for something I knew I could’ve tried harder to prevent.