OBVULATION

Been trying to conceive past 2 months 

I finally bought obvulation tests to help me along plus tracking symptoms on 2 different sites I have been taking obvulation tests every day in my fertile window but all have come back negative I feel like I'm obvulating is it possible I'm not taking them right I'm due for my period on 23/12/15 so technically I should be obvulating today as its 2 weeks before my next period HELP PLEASE !!!