So I'm over a month late for my period and I have no idea why. I'm not pregnant(got a blood test done at the OBGYN just in case), I'm not stressed, I haven't gained or lost any excessive weight and I don't exercise. The last time I had it was painful and short and the time before that it was two months long. I asked my doctor what it could be but she didn't have many answers for me. Has this happened to anyone before? Oh also I'm on birth control but I have been since 2012. Help?