Yes, you can use Clue Conceive if you have unpredictable cycles. While the algorithm behind Clue Conceive works best for people with cycle lengths between 20-40 days and cycles that do not vary by more than 9 days, anyone can use the mode regardless of their cycle length or variability.
If you experience unpredictable cycles often, it may be helpful to see a healthcare provider to get more information on this as you try to conceive. Unpredictable cycles are common, but may need to be evaluated to help you identify the best days in your cycle to try to conceive.