This happened to me after my miscarriage too. I finally asked my Dr and she said that I could be having Chemical Pregnancies... where you get pregnant but miscarry before implantation. She gave me a bunch of blood pregnancy tests to do which are more sensitive than the pee sticks. I did them all during months that I was convinced that I was pregnant not one came back positive.

Eventually I took a spiritual healing course and found that my mind and my body had become disconnected through the stress and hurt I had been through with the miscarriage. I began meditating with the guided fertility meditations from www.anjionline.com and the symptoms cleaned up... so much in fact that 3.5 months ago I was wondering where my period was and I did a pee test with out expecting any kind of outcome and there to my surprise I saw that I was (and still am) pregnant.

This was my journey, it may not be yours but I wish you all the best of luck with your desire to have a baby.
N