So I have my period every month, but it is usually a week late. I had sex with my then boyfriend in August. I had a heavy period in September, but I haven't had one in October. I am now two almost three weeks late. I took a pregnancy test and it was negative..and I have had PMS Symptoms like mood swings, head aches, and food aversions/getting full easily(Like I could eat a muffin and be full for the whole day), but no period. I looked up reasons why my period could be late, but I don't really match up to any of them...can anyone help me?