Stress is a factor too when you want it so much you cause yourself undo Stress and then you can make yourself late. Sadly there isn't alot you can do besides keep trying and remember to have fun while trying.
I have done everything and I just started this morning.....
Sometimes it just takes time. You might want to start taking prenatal vitamins and tracking your ovulation, if you are not already doing so. Also, you might consider going to the doctor just to ensure that everything is okay.
Good luck! :)