My periods have been very predictable about when they are going to start. Because of that just to help me out knowing when they're going to start and when I'm ovulating, I got a period calendar app. on my phone. For the 3-4 months I've used it, it has been exactly spot on about when I start my period. This month on 5/13/14 was the day I was supposed to start my period. I went to the bathroom and then one time there was one little thing of blood mixed with some kind of fluid to make it stringy and then that was it. I put in a tampon because I thought that was me starting my period but when I took it out to change it, there wasn't any blood on it. Just a little light brownish color on the tip. No other bleeding or signs of bleeding from then on and today is now 5/15/14 and still nothing. I tried looking up why it's going on like this and all I'm getting is "implantation bleeding." Should I go take a pregnancy test or what? THANKS. (p.s.-me and my fiancé have been having unprotected sex and trying to get pregnant)