I have a few apps and one told me I ovulated on the 13th another said I ovulated on the 17th I had unprotected sex on the 13.

Another one told me that I ovulated last Saturday so the 24th I had sex on that day.

I have never been pregnant and I'm am 20 I have gone to the doctor's and they done an ultrasound for me and said nothing was wrong with my ovaries and stuff I then had blood tests done for thyroid problems and all of that and the only thing that they said was wrong is my folic acid was down I am 4 days late but my periods are irregular