You might as well do teshuvah anyway!
As the Gemara says, do teshuvah the day before you die (that is, since no one knows when they will die, we must do teshuvah daily). And why omit mentioning something in your daily teshuvah just because there is some doubt about whether you did it?
Of course, after doing teshuvah you can add a prayer to help you keep track of and remember your actions!