Coming off the pill...

I stopped my birth control pills (which I've been on for 12 years) in mid August and had my usual period a few days later. My husband and I are trying to conceive baby #1. I have had no period since then, and pregnancy tests are definetly negative. I've been to my Dr. who says if I don't have my period by the end of the year to come back in. I have had cramping multiple times and was sure I was going to start but haven't. Has anyone else has this problem, feeling like you are going to start but don't? Long story short, until I begin having my period again and ovulating, no chance getting pregnant anytime soon...it's very frustrating.