Sometimes even if the first cycle seems normal, you start to see your cycles elongate or shorten. First remember that your cycles have changed now. Every pregnancy, regardless of outcome, changes your hormonal makeup. As long as your cycles are at least 24 days and not more than about 45, you are in the range of normal. Your cycles do not have to be the same every month, and most often they will not be.
About 60% of women will get pregnant again within the next four months, especially with earnest work toward that goal with the help of the Sperm Meets Egg Plan. Your fertility may not return immediately, but you should hold off on Clomid or other reproductive assistance for six months. After that point, you can ask for help from a doctor to see what is going on. It is not unusual to meet women who tried for a year before getting pregnant again. I personally did not ovulate in my first two cycles following my miscarriage, and got pregnant first try on the third.
It is very disheartening to see month after month go by without getting pregnant again, especially when your cycles are not the same as before. You will constantly feel you are pregnant but test negative, and you will feel certain you are having early miscarriages. This is a very very common feeling, but usually it is not true.
You will also face another problem. Post miscarriage cycles are all over the place, sometimes coming on day 22 (making women think they have a luteal phase defect) and other times coming weeks late (making women spend a fortune on pregnancy tests.) This is all a very common scenario in the months following the loss. It happened to me too. Just keep trying, and trust the pregnancy tests. They are accurate. Your hormones right now, however, are not. You should call a doctor when you go for seven weeks without a period. They can (sometimes, if they will) put you on a dose of Provera to bring on a period, or if worst comes to worst, put you on birth control pills to regulate you.
At this point, you are ready to look over the Trying Again section.