Missed Period - Not Pregnant, HELP?!

I am pretty positive I experienced  chemical pregnancy in September. In October I was almost two weeks late for my period so I excitedly took an at home pregnancy test. It was negative. A few days later I took another one. Still negative. I have still yet to get my period and I am trying not to freak out because I have never missed a period before. I'm 25, and have always been extremely regular. Do you guys think the chemical pregnancy could have messed up my cycle? How long do you go without a period before you see a doctor?