I know that certain positions make it more difficulty for a woman to get pregnant. Maybe you should try changing up your positions and see if that helps.
if your stressing to much this can be a factor, i've been ttc for 2 and a half years with no luck and our fertility treatment all came back fine as well there are no problems for us either. I know everyone say's it and you get fed up listening to it but try and relax and not think about it to much, have fun BD and don't turn it into a chore.
It does take a normal, healthy couple up to 2 years to conceive. i wish you all the luck in the world and hope you get your BFP sometime this year, i know how disappointing it can be seeing a BFN every month!!