Has anyone ever used the ovulation calendar?

Not sure how to start this ...

I’m 22 years old. I had lost my virginity to my boyfriend at 21. We have been together for a little over a year now . I guess you can say things got pretty wild after experiencing intimacy. Less than a year I had taken 4 plan b’s ( 2 condoms broke, the other two was us being irresponsible, also I don’t want to take anymore leading it to harm my body in some way), and have never taken birth control (because I don’t want my body to change or depend on it ). I have now started using the ovulation calendar and took an ovulation test. The calendar came out to be accurate with both my period and ovulation . I have been using the app to prevent pregnancy. He has came in me twice, four days after my last ovulation day. Has anyone else found the app to be accurate ? Or inaccurate ?