I'm not sure how this goes but i have never been the type to count my cycle, when it comes it just come! but recently me and my partner have been having unprotected sex and i thought he was pulling out, but i found out he have not been. I downloaded this app that predicts your period and your ovulation and everything but the thing is i never counted days in between my period so im thinking that its doing a 28 day count! the only period i can remember was the one i had on the 15th of feb so that what i logged in on the app and it shows that i have missed my period may 8th and today its 5/14/15.. I took a pregnacy test yesterday that showed a negative sign so im trying to figure out can i trust this app, because i have the cramping and there is still no period! can any one suggest anything