5 months off of birth control and only one period

I'm 26 years old and I have been taking birth control on and off since I was 15 years old. For the last three years I have been taking my birth control pills (Microgestin) straight through as to not get my period each month. I was doing so because I get really bad cramping, a really heavy flow, it knocks me out for the first three days, I get extremely moody, and it lasts 7 days. I was diagnosed and treated for Pelvic Inflammatory Disease in March of 2010 which was NON STD related. I still continued to take my birth control straight through during this. I discontinued my birth control five months ago in June 2011. I didn't get my period until August 24 2011 and I haven't gotten my period since. At first I thought I was pregnant because during the month of September because I was feeling dizzy, nauseated, headaches, light cramping, etc. but all home pregnancy tests came up negative. Do I have a hormone imbalance that's causing a loss of a period? Could it be related to P.I.D.? My fiance and I would like to have a child before I turn 30 and now I'm a bit concerned that I won't be able to conceive.