I took Plan B about 3 weeks before my last period and I think it screwed me up. I had a period I guess but it was just brown for a couple of days followed by bleeding so light. I didn't even bleed through a whole regular tampon. Well I'm near my ovulation but for almost 2 weeks I've been cramping with lower back pain and just feeling generally tired. I took a pregnancy test a couple of days ago and it said negative. I left it out on the counter and saw it a little later and it had a faint positive line. I took another test and it was negative. Has anyone had this happen before expecially after plan b?