What Causes A Missed Period,vaginal Discharge And Negative UPT?

No periods till now. Used Preganews to test with first morning sample on 20th January 2012. The result turned to be negative.Basic Details:-Last menstrual Period:- 07th December 2012General Cycle length:- 25 days for last three periods, or else generally 28-30 days Had Sex on 12th December 2011 & 2nd January 2012 (Penetrative Sex but no ejaculation inside)General features with me:-Generally face thick white discharge at time of ovulation, this time had the jelly white discharge on 17th December 2011. Generally 14th day after discharge i get periods, so i think this to be a discharge for ovulation.Abnormalities this time:-I had a spot of drop of blood or brown / dark red discharge on 22nd January 2012. I saw this on my panty, and not very sure if it is blood but near to sure that it was blood. I never have these kind of discharges. No other symptoms of cramp or nausea or anything. Aroudn the time of periods (i.e. 2-5th January 2012) i used to feel i am getting periods but never got it.I am really fuzzed as i am engaged and getting married in April 2012. Dont want to create a scene and dont want to be preganant, tell me what to do? Dont want to take risk of consulting a doctor as town i live in is small town and dont want to be exposed.