To know when you are ovulating, you should do two things everyday. First, take your basal body temperature every morning. Remember to take it everyday at the same time and before you get up from bed to do anything. Then you should check your cervical fluid. We all know that once your basal body temperature rises more than 1/10 which means you have already ovulated and it will be too late to try for baby. So you should observe your cervical fluid everyday. Once you see your cervical fluid getting like "egg white" which is strechy and wattery, it is the best time for you to have sex. Usually you will have the egg white cervical fluid before your ovulation. Keep trying until you see your temperature rises.
There is a very good book called "Taking Charge of Your Fertility" by Toni Weschler. You can read all the things about how to find our when you are ovulating and to understand your cycle better. I strongly recommend all girls to read this book.
I have been taking BBT, observing cervical fluid and using the ClearPlan for months. Yet I've found some inconsistence in these 3 things in my case.....the BBT did not drop over 1/10 (but it's in normal low level, not as low as 36.1 or so) when the fluid is abundant and stretchy, and when the ClearPlan left line turns blue to similar to the demo line. And after ovulation (if I take the fluid and Clearplan as indication of ovulation), the BBT did not rise drastically. It rises bit by bit, may be about 3 days later, it rises to 36.7 or 36.8.
Sometimes our bodies don't react in a perfect way. First of all, the ovulation prediction pack cannot be trusted 100%. You have to understand that even if it shows that your LH level rises but it doesn't necessarily mean that you are ovulating on that day. You should have keep trying since you see positive result from the prediction kit until you see your body temperature shift high. Once your temperature shift then it means that you have already ovulated. Second, it is good that you have been observing your cervical fluid. In order to get pregnant, your cervical fluid has to provide a optimum environment for the sperms to move to seek for the egg. Hence if you notice that your cervical fluid is not at optimum stage (like egg white) then I'd suggest you take some Robitussin (be sure to use plain Robitussin, since other types can dry up your cervical fluid) starting several days before your anticipated ovulation thru to the first day of your temperature shift. It will help to make your cervical fluid wetter.
Again, I think you will find the book "Taking Charge of Your Fertility" by Toni Weschler, MPH. I have learned a lot about my own cycle and how to find out when is the optimal time to try for baby. See if you can find it at the bookstore. I hope it is helpful to you.
Mao, I am glad that I can help. I am not so knowledgeable but I like to read a lot of books. I noticed that it is not so easy to find a well written book about fertility or pregnancy in Chinese. So I started to look around for English books and I found that there are a lot of good books out there. Plus, it is good to talk to your doctor and ask questions. Once you have been knowledge about your own body, you will feel a lot more in control.
Remember the most important thing is to relax and stay happy. If you are too anxious, it is not going to be good for your health. Good luck.