how accurate are period tracker apps on iphones? could i be pregnant?

[LayneBryant]

i use an app to keep track of my periods. ive only used it for the last few months. and last month i was a day early on my period then from what it said. now it says im two days late and im freaking out that im pregnant! i havent felt sick, my boobs are not sore. i took a test yesterday and it was negative. missing my period is the only reason i think i am. me and my bf have unprotected sex. he pulls out.

 

[booboo]

I use period tracker for the iPhone and its been pretty on the spot it took some time to get the settings right for me but after that I love it and could no live with out it but only 2 days is not that late so I would just wait a week and if aunt flow don't visit you then take a test

 

[Ashley]

They're pretty simple. They work on a 28 day cycle, unless you put in otherwise. They say day 1 get your period. Day 14 you ovulate. Then day 28 you should get your period the next day. They're pretty accurate if you have a regular cycle, they track the same way you would on a calendar or just in your mind. Just because you're a few days late, doesn't mean you're pregnant. It could be completely normal. I would wait a few more days, if it doesn't come test again. Good luck.