No need to apologize – the site is meant for women to be able to ask such questions.
A woman becomes niddah if there is bleeding from the uterus into the vagina, even if it never exits the body. Therefore, the internal hefsek taharah examination, which confirms that bleeding has ceased, is mandatory. It is not sufficient to just rely on a lack of spots on clothing.
After the hefsek taharah, you need to count seven clean days during which at least a minimum number of bedikot must be performed. Please read more about the hefsek and bedikot (how to do, when to do, etc.) on the site and get back to us if you have additional questions.