If you become ineligible, you can no longer use Clue Birth Control as a birth control method. Clue Birth Control will not be able to calculate your risk for pregnancy. You have to use a barrier method such as a condom every time you have sex that may result in pregnancy.
To continue tracking your period, learn about your cycle, and discover patterns, you can easily switch to Clue Period Tracking mode. Meanwhile, it is advisable that you speak to a healthcare provider about alternative birth control methods.