If you haven't got your period then you are on cd 29 today. Your cycle only lasts as long or short as the time between the first day of your last menstrual period and the day before your next one. Does that make sense? HAve you always been regular to the day, or give one or two days? No matter what you are on cd 29 today, unless you get your period, then you'll be on cd 1.
This is correct - if you haven't got your period today then you will be on CD29, regardless of how long your cycle is normally. If you got your period today you will be on CD 1. So, the question is have you got your period today? If you have then you will need to amend your cycle start date in the ticker.