Are the days of fasting that I intended voluntarily, if they were not obligatory, counted, knowing that the accountability may not only be due to menstruation?

If you doubt whether puberty occurred before menstruation, the default is that it did not. Therefore, you are not required to make up any prayers or fasts. However, if you fasted as a precaution, and the fast was not obligatory, its reward will not be lost; rather, it will be considered a voluntary act for which you will be rewarded.