pregnant despite contraceptive computer

I wanted to upgrade to a hormone-free contraception and have decided after a long search for the cyclotest 2 plus. The instructions are easy to understand, the device can be easily operated and thanks to the software (the CD is unfortunately quite expensive and you have to order extra) you can let the cycle still evaluate on the computer. So I was surprised equal positive and very satisfied with the device ... but it has only about 9 months done that for which it is chamber, namely to help in the prevention. Although I have therefore kept me very closely to the instructions and have directed me strictly according to the photos displayed on the device, which indicate whether you can just get pregnant, I'm still become pregnant. One should therefore before engages be clear whether one would clear with a pregnancy or not to the device. Because if one is really 100% sure not to get pregnant to want here is simply too great a risk that the desired goal is not achieved. So then would you prefer looking for a safer method of contraception.